92 STUDIES ON THE ELASMOBRANCH SKELETON, 



length. The latter support the end of the groove of the clasper, 

 and by their rotation can open or close it. 



The pelvic arch is narrow from side to side and very long 

 antero-posteriorly — the greatest breadth being only about twice the 

 length — convex ventrally, convave dorsally. 



Unpaired Fins. 



The dorsal fin is very simple, consisting of two broad and thin 

 sheets of cartilage, an anterior and a posterior ; the former much 

 the larger, having about 17 few-jointed rays united with their 

 upper edge. Several of these rays are obscurely bifiurcate. This 

 is very similar to the dorsal fin of H. chiereus* except that the 

 posterior basal cartilage in the latter is very small. 



The anal fin is similar to the dorsal, but smaller and with fewer 

 and shorter rays. 



CROSSORHINUS BARBATUS. 

 Plate I., Figs. 6-8 and Plate II, Fig. 13. 



Skull and Visceral Arches. 



The cranium is very wide and depressed, as in Scyllitcm catidus, 

 the interorbital breadth being relatively much greater than in 

 Chiloscyllium. A noteworthy point in comparison with related 

 genera is the much greater relative antero-posterior extent of the 

 post-orbital region. The occipital surface slopes upwards and 

 forwards, and meets the upper surface in a rounded ridge, in front 

 of which the not very deep pai'ietal groove is situated. The upper 

 surface of the skull in front of this is marked by a shallow mesial 

 longitudinal depression, the continuation forwards of the parietal 

 groove ; it is bounded externally by a continuous raised border as 

 far as the pre-orbital process. 



The occipital region is not produced in the middle line behind. 

 As in ScylUum, Mustelus, Galeus, and Scymnus, the lateral posterior 



*Mivart, 1. c, p. 443, pi. LXXV., fig. 2. 



