Descriptions on Unidentified Species of Dibranchiate
Cephalopods.
II. A Cranchiidae Squid of the Genus Taonius.
ByEm lWAI(Laboratory of Fisheries Zoology, Faculty of Agi-iculture, Tokyo University.)

A good specimen of this deep-sea squid was given to the author
through the kindness of the Whale Research Institute.
As would be described later in this paper, a member of characters
go to prove definitely that this species belongs to the genus Taonius of
the family Cranchiidae. Two of the striking characters are its elongated form and the soft gelatinous like nature of the body. Many othercharacteristics were observed while comparing it with the known species
Taonius 'fXJ;VO. As the present writer is not aware of any literature ofthis specimen and its differences and similarities with other known
species, he has made and effort to publish here the observations hemade on this unidentified species.
The sample was obtained from the stomach contents of the sperm
whale caught near Kamchatka in the North Pacific in the summer of1951.
The writer wishes to express his sincere gratitude to Dr. M. N1smWAKI for supplying the sample, to Prof. M. ISHIKAVvA and Y. SUYEHIRO
for the valuable guidance rendered during the course of the work andlast but not the least to Assoc. Prof. T. HIBIYA for reading the proofof this paper.
General descriptions of the specimen
Mantle and its surface: Mantle texture remarkably characteristic;
very soft and gelatinous as in Chiroteuthis. The body form of thisspecimen is much elongated, subfusiform, and its length is about 7times the maximum breadth, which is perhaps at the anterior portionof the mantle. From this region the mantle gradually tapers behindnear up to the beginning of the fin and then becomes narrower rapidly,
to continue as the filiform end-process (figs. 1 and 2). In this point,
the sample almost resembles Taonius 'JXl;VO. The ' Schwanzfaden ' as
described by PFEFFER on the VERRILL's and JoUBIN's specimens of T.
pavo, does not exist in this sample.

154

E. IWAi:

In table 1 are collected the results of the morphological measurements made on the sample.
Table 1. Morphological measurements of the specimen examined.
Body parts

LengthMantle; ventral length
breadth at the .anterior margin
Fin;
lengthmaximum breadth
Head;lengthbreadth except the eyesheightArms;

length of the firstthe second
the third
the fourthEyes;
diameterFin length/Mantle length
Fin length/Fin length-----~-----

left
94
124
120
114

428mm
63
164
76
47
27
33
right
*76
120
123
113
3739%
218%

--------* the tip broken

It is a very striking fact that on the surface of the mantle aredensely scattered white hemispherical crystalline tubercles of about 5
to 7 mm. dia. and many black large and smallpi gment spots of lessthan 5 mm. quite differing from the chromatophores in the generalsquids (fig. 3). They are about the same in arrangement and number
at both dorsal and ventral surfaces of the mantle except at the attaching portion of the fin, and on the whole they become more abundant,
distinct and larger as the anterior mantle margin is approached. However, no tubercles are recognized on the surface of the fin and themantle region situated along the fin. On the other hand, black-coloured pigments do not at all exist on the ventral side of the fin and thedistribution on the dorsal surface is limited only to the gladius region.
It is of great importance to note that there is not a single line ofchitinous tubercle on either side of the ventral aspect of the mantle.
As in general Cranchiids, the anterior margin of the mantle isfirmly fused with the head by the cartilaginous articulations, indirectly at both the funnel bases and directly at the nuckal region. At
these points, the mantle is faintly convex with a dune crescentwise
angle.
Fin: As regards the combined outline of the fin, it is a littleDescriptions on Unidentified Species of Dibranchiate Cephalopods

155

elongated and gold-coin shaped with a projected extremity; its lengthis decidedly more than twice the maximum breadth. Since there is noappearance of the anterior insertion, lateral angles and auriculating
lobes are not distinctly recognized.
Head: The head proper excluding the projecting eyes is rather
narrow and triangular shaped when looked from the ventral side; on
all its surface, no kinds of tubercles or folds are found. There is aclear demarcating constriction between the head and arm regions. The
dorsal surface is roundish and smooth. The ventral side is almost totally occupied by the expansion of the funnel. The eyes are enormously
large, and projected from the lateral surface of the head by means ofa short but thick peduncle ; the diameter of the eye reaches about 35mm. and it is about 30 mm. in height. In SASAKI's text-fig. 145, theeyes are not so much protruded as in this specimen.
At the posterior margin of the eyes, olfactory tubercles are situated in T. pavo, while in this specimen a gelatinous substance surrounded by a yellow-coloured band in formalin fixing solution is found near
the same place. The author is not certain whether this is the sameas the olfactory tubercles of T. pavo.
The funnel covers almost the whole ventral region of the head andis between two linear elevations of the cephalic cartilage running along
both the ventral margins, and is especially expanded at the base inlongitudinal directions. The figure of this is shown in fig. 5; the distal
part, free from the head, is much longer, when compared with common squids and its orifice is vertically opened. The funnel groove isnot well differentiated. The olfactory crest is also not distinct.
Arms : Arms not equal in length and are rather short. The
length is about one-fourth the length of the mantle; their order oflength being 2 ·. 3 ·. 4 1. The thickness of the arms are more or lessalike, and are round in cross-section. The arm tapers gradually fromthe base towards the tip, and its distal end is blunt.
The keel nor the web are developed in any one arm. However,protective membranes are well developed and extend from the proximalbase to the distal extremity along the two sides. The dorsal membrane
is much smaller than the ventral one. The width of the ventral membrane reaches about 10 mm on each arm. SASAKI, however, in hisdescription has said that the proximal half of the third arm is slightly
keeled and the dorsal outer surface of the fourth arm is webbed. The
trabeculae are thickened.
Arm suckers: Arm suckers are globular and relatively large. They
are arranged in 2 rows throughout. They begin from the basal end
and are distribute at some intervals at the proximal region, but are>

E. lWAI156

crowded at the distal portion (fig. 6). The suckers are almost the samein size and structure at similar regions in each arm. The suckers are
smallest on the ventral arms. Choosing the lateral third arm for thedescription of suckers, there are about 50 pairs of suckers arranged in
2 distinct rows. The suckers of the 9th or lOth series are the largest
and those following are similar in size. Again the suckers of the 17thor 18th series are remarkably large and those that follow become
gradually smaller in size. However, when the size of the distal suckers
compared with those of other common squids are comparatively larger.
A similar feature is observed in all the other three arms (fig. 4). SASAKI's specimen had 20 pairs or more of suckers.

abc

Text-fig. 1. The structure of 3 kinds of horny rings on the suckers of the left
third arm. (a) The proximal one; lst series. x20. (b) The central one; 13thseries. x20. (c) The distal one; 25th series. x20.

Generally, the structure of horny ring is related in its proportion
to the size of its bearing sucker. Namely, three kinds of teeth wereseen (text-fig. 1). The proximal horny ring is provided with 3 to 5
square-cut teeth produced from the higher wall of the horny ring. The
teeth of the other horny rings are also produced from the same higher
wall region. The teeth of the proximal horny ring are closely set byeach other with deep crests.
The central horny ring which is the largest has about 7 to 12
teeth, much broader and shorter than the former, so much so thatthey are easily over-looked if carelessly observed. It was also observed that some erotion into the wall usually occurred near the marginal
teeth and sometimes an irregular bridge at the opposite side of theteeth region was seen.
In SASAKI's specimen, teeth was produced on the whole margin of
the horny ring and it numbered about 20 to 30. But according to
VERRILL's and JOUBIN's descriptions, teeth were present only at theDescriptions on Unidentified Species of Dibranchiate Cephalopods

157

higher wall as in this specimen.
On the distal horny ring, situated after the 20th series of suckers,
the number of teeth is considerably decreased to 4"-'6 and its form becomes conspicuously sharp and triangular in shape. Besides these, afew anomalous plate-like teeth were also seen at both lateral sides of
the horny ring.
Tentacles: PFEFFER described that tentacles are easily broken. To
my regret they were completely lost in this specimen.
Buccal membrane: The buccal membrane is rather thick, broadand supported with 8 ribs, of which the dorsal and ventral ones areunited at the base and are T-shaped. They are further fastened tothe dorsal side of the second arm and to the ventral side of the thirdarms. The outer lip is well developed.
Gladius: The gladius is dark amber-coloured and clearly perceptible from the back of the mantle. It extends over the whole length ofit. The basemental structure of the gladius resembles well with thatof T. pavo. The anterior half of its gladius is followed behind inequal width, and while leaving the middle region, it spreads by degrees
posteriorly and then from the origin of the fin, it rapidly tapers, forming a filiform end-cone at the distal end.
Conclusion

In M. SASAKI's monograph on the Dibranchiate Cephalopods, singlespecies belonging to the genus Taonius, in the sea-around Japan wasrepresented. In foreign countries, several species were described since
STEENSTRUP's introduction of this genus in 1861. Later, it was clarified that they belong respectively to other new genera, expecting thespecies which is quite similar to T. pavo. As far as the author is awareof, there are no other species of the genus T. pavo anywhere. The
author believes that the specimen described here is the only species ofthis genus ever found, in view of the following reasons :(1) Is most elongated.
(2) Length of mantle, fin, head and arms is proportionately similar
to that of T. pavo.
(3) Galert-like consistency of body constitution.
(4) Non-stalked large eyes.
(5) Structure of lanceolate gladius.
On the other hand, remarkable difference with T. pavo were also
seen as shown by following characters.
(1) Existence of white tubercles and many kinds of pigment spots
on the surface of the mantle.

158

E. lWAI(2) Situation of teeth on the horny ring of each sucker and its
number,(3) Absence of olfactory tubercles.
(4) The curious tongue-like shape of the funnel and its verticalopening.
Among these, it is the most notable fact that the specimen has
Calcium hyaline tubercles which are not found in other Taoniinae squids
and appearance of them suggests the close phylogenical relationship to
the Cranckiinae squids.
Many important questions remain unanswered and due to the lackin number of the samples, it seem almost impossible to establish a new
species now. However the author hopes that the work on this unidentified species would be continued by others interested, and definite conclusions come to later with the establishment of the new species.
References
HOYLE, W. E.: On Loligopsis and some other Genera. Proc. Roy. Soc. Edinburgh 8, 313333 (1885).
-~ --:
Report on the Cephalopoda collected by H. M. S. CHALLENGER during the Years
1873-1876. Edinburgh 1-246 (1886).
JOUBIN, L.: Cephalopodes provenant des campagnes de la PRINCESSE-ALICE (1891-1897).
Result. Camp. Scient. Albert I de Monaco. Fasc. 17, 1-135 (1900).
LESUEUR, C. A.: Descriptions of several new Species of Cuttle-fish. Jour. Acad. Nat. Sci.
Philadelphia 2, 86-101 (1821). (not seen original)
PFEFFER, G.: Die Cephalopoden der Plankton Expedition. Ergeb. Plank. Exp. Humboldt·Stiftung., 2, Fa, 1-815 (1912).
SASAKI, M.: A Monograph of the Dibranchiate Cephalopods of the Japanese and adjacent
Waters. Jour. Coll. Agric. Hokkaido Imp. Univ., 20, Suppl. No. 1-357 (1929).
VERRILL, A. E.: The Cephalopods of the North-eastern Coast of America. Transact.
Connecticut Acad. 5, 177-446 (1881).

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