Q: In this task, you will be given a passage to read. A fill in the blank question will be given to you. Your answer should fit the blank appropriately.
The pectoral fin disc of the plain maskray is thin and diamond @-@ shaped with narrowly rounded outer corners , measuring 1 @.@ 1 1 @.@ 3 times longer than wide . The leading margins of the disc are gently concave and converge at a broad angle to the pointed tip of the snout . The small eyes are placed close together , and behind them are the spiracles . The nostrils are elongated and have a skirt @-@ shaped flap of skin between them . The small mouth bears prominent furrows at the corners and contains two slender papillae on the floor . Small papillae are also found around the outside of the mouth . There are five pairs of gill slits . The pelvic fins are fairly large and pointed .The tail is short , barely exceeding the length of the disc when intact , and has a broad and flattened base leading to usually two stinging spines . After the stings , the tail becomes slender and bears a long ventral fin fold and a much shorter , lower dorsal fin fold . Most of the body lacks dermal denticles ; a midline row of 4 13 small , closely spaced thorns is present behind the spiracles , and another row of 0 4 thorns before the stings . The dorsal coloration is grayish green , becoming pinkish towards the disc margins ; there is a dark mask @-@ like shape around the eyes and a pair of small dark blotches behind the spiracles . The tail behind the stings has alternating black and white bands of variable width , ending with black at the tip . The underside is plain white and the ventral fin fold is light grayish in color . This species grows to 24 cm ( 9 @.@ 4 in ) across and 45 cm ( 18 in ) long . fill in the blank : The pectoral fin disc of the plain __________________ is thin and diamond @-@ shaped with narrowly rounded outer corners , measuring 1 @.
A:
maskray