4 o ZOOTOMV. 



extremity of its anterior edge, and an iliac process (i/) 

 directed upwards and backwards from the external extremity 

 of its dorsal surface. 



51. The acetabular facets (Fig. 10, ac. i, ac. 2), two 

 projecting convex articular processes on the extremities of 

 the hip girdle, the anterior being directed outwards, the 

 posterior backwards. 



52. The basale metapterygii, a stout backwardly- 

 directed cartilage, articulating with the posterior acetabular 

 facet : it is continued by smaller cartilages to the posterior 

 point of the fin. 



In the male this series of cartilages is directly continued into the 

 skeleton of the claspers (see 57), which is composed of several 

 more or less calcined cartilages, some of them produced into sharp 

 processes of various forms. 



53. The fin rays : the first four or five are attached to 

 the pelvic girdle, pass almost directly outwards, and support 

 the anterior lobe of the fin ( 56); the first, or pre-axial 

 ray, is many times thicker than any of the others, and 

 articulates with the anterior acetabular facet : the remaining 

 fin rays are connected with the basale metapterygii, pass 

 outwards and backwards, and support the posterior lobe of 

 the fin. 



B. DIRECTIONS FOR DISSECTION. 



XI. Verify the following external characters :- 



54. The extreme depression of the body from above 

 downwards : its rhomboidal shape, the anterior angle of the 

 rhomboid being formed by the snout, the lateral angles by 

 the points of the pectoral fins, and the posterior angle by 

 the root of the tail, which is slender, depressed like the 

 body in its anterior part, but compressed from side to side 

 posteriorly. 



