BY WILLIAM A. HASWELL, M.A., B.SC. 01 



Hexanchus griseus.* The intercepted cartilage is temptingly like 



a presternal, but the absence of such an element in the skeleton 



of any group nearer than the Amphibia seems to preclude this 

 explanation. 



The Pelvic Fins. (Plate L, fig. 3.) 



In the pelvic fin of Heptanchus indicus there are three distinct 

 basal cartilages articulating with the pelvic girdle and bearing rays ; 

 these represent the prse- meso- and meta-pterygia of the pectoral 

 fin. The first (p. pt'.) is the ecpuvalent of the so-called pre-axial fin- 

 ray. It is a small, pointed cartilage articulating with the antei'ior 

 facet on the pelvic girdle, curving forwards and outwards and 

 ending in a pointed extremity. By its outer posterior border it 

 gives attachment to the four anterior fin-rays, of which the first two 

 have their bases coalescent. The mesopterygium (vi.pt'.) is a small 

 cmadrate cartilage articulating with the middle facet of the pelvic 

 arch, and giving attachment to two fin rays f The remainder of 

 the rays are attached along the outer border of the metapterygium 

 (nit. pt'.) The latter is a long narrow cartilage, somewhat curved 

 outwards. Distally it gives attachment to two cartilages ; of these 

 that situated more dorsad is a small nodule, articulating with which 

 is a long narrow ray-like cartilage ; the latter is applied closely to 

 the dorsal surface of the cartilage of the clasper and strongly 

 united with it by means of fibrous tissue ; the more ventrally 

 placed of the two cartilages articulating with the extremity of the 

 metapterygium continues the axis of the fin, gives attachment at 

 the base of its outer border to the last of the fin-rays, and distally 

 is succeeded by a smaller cartilage with which the principal 

 cartilage of the clasper articulates. The axial cartilage of the 

 clasper is a slender, slightly curbed cartilage, which presents no 

 appearance of the longitudinal groove found in Crossorhinus. 

 Distally it supports two small, blade-like freely movable ossified 

 cartilages which are attached to its apex about the middle of their 



* Gegenbaur, Schultergnrtel der Wirbelthiere, Op. cit. Heft. 2. 



t If this middle basal cartilage is present in the European species it has escaped notice. 

 (See Davidoff, Alorph , Jahrb. V. ; Mivart, l.c,p. 444, pi. LXXV., flg. 4.) 



