535 MR. A. s. WOODWARD ON [Dec. 7, 



ment. The latter {mtp) is triangular in Ibrin, and elongated antero- 

 posteriorly ; the foremost border abuts against the hinder edge of 

 the preaxial cartilage, which it equals in transverse extent ; and the 

 inner border curves gradually outwards and backwards to meet the 

 nearly straight external boundary at a posterior apex. Judging from 

 the analogy of living Selachians with fins of a similar type, the 

 posterior of these cartilages may be regarded as the metapterygium ; 

 while the anterior element may represent the coalesced pro- and 

 mesopterygium (as in Pristiophorus^), or it may be wholly meso- 

 pterygial, with a minute, indistinguishable propterygium at its 

 proximal angle (as in Heptanchus and Hexanchus ) . 



Beyond the basal cartilages are arranged the cartilaginous rays of 

 of the fin (?•). These are somewhat obscured both in front and 

 behind by remains of the integument, and it is uncertain whether 

 the first attached to the preaxial element is stouter than the remainder ; 

 twenty rays, however, can still be counted on the right side, and 

 there are traces of sixteen on the left ; the foremost thirteen are 

 directed almost transversely or outwards, while the following have a 

 more marked backward inclination. 



The pelvic girdle and its appendages are rather more satisfactorily 

 displayed than the pectoral structures just described. Anteriorly, 

 on each side, the cartilage is prolonged into a remarkably strong 

 prepubic process (p-pb), the base of which occupies one fourth of 

 the entire breadth of the girdle ; but the forward extent of the 

 prominence is not determinable, owing to imperfect preservation. 

 Posteriorly, on each side, is a long slender iliac process («7), especially 

 well seen on the left, and slightly directed outwards ; it is much less 

 robust than the prepubic, and appears of almost uniform breadth 

 throughout ; in length it equals twice the width of the transverse 

 pubic cartilage (pub). Arising immediately within the point of 

 iniion of the pubic and iliac regions is the basal cartilage {b.s) of 

 the pelvic fin, which exhibits no sutural divisions, and (this specimen 

 being a male) is prolonged backwards into a powerful clasper (c/). 

 It curves gradually inwards throughout the whole of its rayed portion, 

 and is of almost uniform breadth. On passing into the claspers, 

 the cartilage becomes more calcified, and perhaps slightly broader. 

 The inner edge is straight, but the outer edge exhibits a gentle 

 sigmoid curve, which results in the widening of the rounded terminal 

 extremity ; and at the end of each clasper (especially the left) a 

 small tuft of dermal booklets {kk) is preserved. The fin-rays (r), 

 which appear to be completely shown on the right, are altogether 

 twelve in number, and the length of the supporting cartilage is 

 scarcely more than one half of that of the appended clasper. There 

 is no distinct evidence of one or more preaxial rays attached to the 

 girdle itself, and the foremost exhibited is no longer than the 

 remainder. 



' St. Or. Mivart, " Fins of Elasmobranchs," Trans. Zool Soc. vol. x. p. 463, 

 pi. Ixxviii. fig.l. 



'■' C. Gegenbaur, " Scbultergiirtel der VVirbellliiore, und JBi-Ui-tflo.sse der Fische," 

 Uiitersucli. vergl. Anat. Wirb. 186.3, pi. ix. figs. 1, 2. 



