APPENDICULAR SKELETON — FISHES 



237 



Poh'pterus (fig. 249, B) has an ossified scapula, the ossification involving the 

 glenoid surface, ventral to which is a coracoidal ossification. Cleithrum and 

 clavicle are fused, respectively, with scapula and coracoid, the cleithrum being 

 the larger and extending over the narrower part of the clavicle. Calamoichthys 

 has no cartilage bones. 



The girdle is relatively smaller in Holostei than in other ganoids, both scapula 

 and coracoid being reduced. Lepidostciis has a sHght ossification around the 

 glenoid surface; it is lacking in Amia. The cartilage has the same fenestra as 

 have sturgeons. Lepidosteus has both clavicle and cleithrum; Amia has but a 

 single bone, probably cleithrum, but possibly containing the clavicle (fig. 249, A). 



TELEOSTS (fig. 250) show considerable differences in the pecto- 

 ral girdles, and many genera need more study. The cartilage girdle 

 is smaller than in Chondrostei. In 

 Physostomes three bones ossify on 

 either side: scapula, coracoid, and 

 a third, dorsal to the coracoid and 

 posterior to the scapula which has 

 been called a mesocoracoid, this 

 not appearing in most other tele- 

 osts. The plate-like scapula is 

 largely dorsal to the glenoid re- 

 gion; it contains the supracoracoid 

 foramen. The coracoid extends 

 downwards and forwards and may 

 aid in supporting the fin. When 

 neither scapula or coracoid connect 

 with the fin, the latter is articu- 

 lated directly with the cartilage. 

 Ventrally the coracoids of the two 

 sides may meet, but sometimes an 

 isolated cartilage intervenes. 



The membrane bones are, in 

 general, like those of the sturgeon. 

 Physostomes have a single bone 

 (cleithrum?) in the position of 

 clavicle and cleithrum of other 

 Teleosts. The clavicles in other groups usually extend medially and 

 forwards and may meet. In some Teleosts, where the body is encased 

 in a firm armor (South American Siluroids, Plectognaths and Lopho- 

 branchs), other bones may He between the clavicles of the two sides 



r 



Fig. 250. — Pectoral girdles of {A) 

 Trigla (Gegenbaur, '64) ; {B) Pleiironectes 

 (Cole and Johnstone, '01), and (C) Gadus 

 (Butschli, '10); D, base oi fin oi Pimelodtis 

 (Gegenbaur, '64). c, coracoid; cl, clavicle; 

 fr, finrays; /, lepidotrichia; pc, post- 

 cleithrum; r, radialia; s, scapula; sc, 

 supracleithrum; sp, spine. 



