Sentence:  "Phylloceras ptychoicum" is one of the most interesting species of all those found in the Kutch Jura, [...] The lobes are most characteristic, and on them the external and first lateral saddle are the most important parts. The external saddle is beautifully symmetrical, finishing in four <WSD>phylla</WSD>, of which the two corresponding ones are equal; the first lateral saddle is also divided into four terminating <WSD>phylla</WSD>, which are, however, not quite symmetrical. 
Meaning of the word marked with <WSD> tags:  A leaf, or something (flat) resembling a leaf.