BY WILLIAM A. HASWELL, M.A., B.SC. 97 



of the fin-i'ays. The mesopterygium consists of one elongated, 

 slightly curved cartilage which bears on the distal half of its outer 

 border a sei'ies of eight fin rays. The metapterygium is long and 

 narrow, and bears eleven rays, a twelfth being borne ]>y the small 

 accessory cartilage at the apex. The meso- and metapterygia are 

 separated from one another throughout a considerable part of 

 their length by a well-marked space. The rays are likewise 

 separated at their bases by well-marked intervals ; distally, how- 

 ever, they expand and become closely apposed, except in the 

 case of about six of the inner rays, each of which becomes shortly 

 bifurcated. The skeleton of the pectoral fin in the nearly related 

 Ginglymostoma differs from that of Crossorhinus in the basal 

 cartilages being relatively sirualler. In the existence of the 

 interval between the mesopterygium and the metapterygium, the 

 latter bears some resemblance to ChezloscyUium ocellatum, as 

 described and figured by Mivart (1. o, p. 448, pi. LXXVL, fig. 4), 

 but the space is very much larger in the latter. 



Pelvis and Pelvic Fin. (Plate I., fig. 8.) 



The pelvic cartilage is nearly straight, flattened from above 

 downwards, and a little expanded at either end. The anterior 

 basal cartilage is small and unimportant ; there is no mesoptery- 

 gium, several rays articulating directly with the pelvis. 



The skeleton of the clasper consists of a long ossified cartilage 

 marked on its dorsal aspect by a deep groove, the lips of which are 

 closely approximated ; this axial cartilage ends distally in a 

 strong pointed spine, articulated around the base of which 

 and ensheathing it are four more or less scale-like pointed bones 

 capable of being divaricated from the axis of the appendage so as 

 to spread out in a l'adiating manner from the base of the spine. 



Unpaired Fins. 



The dorsal fins are of nearly equal size ; the anterior contains 

 fourteen, the posterior fifteen rays, each, except the first two or 

 three, with an expanded upper or distal piece, and each, with the 



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