238 VERTEBRATE SKELETON 



and may even extend over them. Clavicle and coracoid are often 

 intimately united. The main part of the cleithrum is dorsal to the 

 glenoid surface, but it may extend down over the upper part of the 

 clavicle. 



The girdle is usually connected with the cranium by one or two 

 suprascleithra, the distal one usually being forked (fig. 250, C) one 

 ramus articulating with the epiotic, the other with opisthotic or 

 exoccipital, and rarely (Cyprinoids) with the first vertebral centrum. 

 In some cases the dorsal supracleithrum is intercalated in the dorsal 

 surface of the cranium, lateral to the dermoccipital and forms the 

 true posttemporal. A few Siluroids lack supracleithra, the cleithrum 

 articulating with the cranium, while in eels, which also lack supra- 



FiG. 251. — Pelvic girdles of (A) Clupea and (B) Amiurus (Kolzow, '96). B, basal;/, fin; 

 m, median crest; mp. median process; pd, dorsal process; pp. posterior process. 



cleithra, girdle and skull are connected only by ligament. Most 

 Teleosts have from one to three postcleithra; when several occur they 

 extend in an obhque Hne downwards from a point behind the con- 

 nexion of cleithrum and supracleithrum. In the 'Thoracici' (p. 228) 

 the lower end of this series may reach the basal ossicle of the 

 pelvic fin. 



In the lower Ganoids and Teleosts a pair of triangular elements 

 extend inwards and forwards from each pelvic fin (fig. 251). These 

 are cartilage in Sturio, elsewhere ossified to varying extents. In 

 most Ganoids (Holostei excepted) they do not meet in the median 

 line, but they are connected in some sturgeons and in Polypteriis by 

 a median cartilage which may represent the true pelvis. In Teleosts 

 the range of form is greater. The basal parts may be connected by 

 ligament or may be in contact. Many have a second process on the 

 medial side, arising at about the level of the articulation of the 



