116 STUDIES ON THE ELASMOBRANCH SKELETON, 



place near the proximal extremity of the latter. The ventral 

 portion of the pectoral arch forms a continuous and rigid bar ; the 

 dorsal extremities of the arch are connected either with the spinal 

 column or with one another. The pro- and metapterygia of the 

 pectoral fins have the form of elongated narrow bars, and the 

 mesopterygium is insignificant. The anterior portion of the 

 pectoral fin is connected by a cartilage — the antorbital cartilage — 

 with the ethmoidal region of the skull. 



Pristid^e. 

 The ethmoidal region of theskull is prolonged forwards into a very 

 long, straight, dorso-ventrally compressed rostrum, traversed by a 

 median and two pairs of lateral longitudinal canals. The first 

 dorsal fin has broad basal cartilages apparently continuous with the 

 neural spines, and a series of short rays. 



Khinobatid^e. 

 The ethmoidal region of the skull is produced into a rather long 

 rostruru. The first branchial arch articulates with the skull. The 

 hyoid arch is not connected with the hyo-mandibular. The 

 copulari of the branchial arches are distinct from the copula?. 

 The dorsal fin has broad basal cartilages, apparently continuous 

 with the neural spines, and a series of short rays. The pectoral 

 arch articulates directly with the spinal column. The pro- and 

 metapterygia are segmented ; between the mesopterygium and the 

 metapterygium a number of the rays articulate directly with the 

 shoulder-girdle. There ai'e well-developed ribs. 



TORPEDINIDiE. 



The ethmoidal region is not produced into a rostrum. The 

 articular surface for the hyo-mandibular is not wide. The copularia 

 of the branchial arches are distinct from the copula?. The hyoid 

 arch is not connected with the hyo-mandibular. The pectoral arch 

 is not directly connected with the spine ; it is not so rigid in the 

 middle ventral line as that of other Batoidei. The anterior portions 

 of the pectoral fins are detached, and articulate with the front of the 

 ethmoidal region of the skull. None of the rays articulate directly 

 with the shoulder-girdle. There are well developed ribs. 





