192 



.SUB-CLASS (AND ORDER) TELEOSTEI 



teeth (Ops). The hypobranchials, which may be wanting 

 in the fourth arch, are attached to a varying number of median 

 elements, the copulae or basibranchia's {Cop). The fifth bran- 

 chial arch is reduced to a single rod on each side which is usually 

 strongly toothed, and the pair are called the inferior pharyngeal 

 bones {Opi) ; they are sometimes ankylosed to form a single 

 bone. The four anterior branchial arches bear small tooth-like 

 projections, in one or two rows, which act as strainers ; these are 

 the gill-rakers. 



Pectoral and pelvic* paired fins are present, but one or both of 



them may be absent. 



In the pectoral girdle, 

 which is usually present 

 even when the fin is 

 absent, the primitive 

 cartilaginous c o r a c o- 

 scapular elements are 

 but slightly developed 

 and relatively unim- 

 portant, while the 

 membrane bones (clavi- 

 cles t) are largely de- 

 veloped. 



Fio. 112. — Right pectoral girdle and fin ot Vadus 

 (after Gegenbaur). c clavicle (rlcithium) ; b 

 supraclavicle (supracleithrum) ; a post-temporal ; 

 d post-clavicle ; / scapula ; e coracoid ; g basal 

 Bomaotids of the fln ; h bony dermotrichla. 



The coraco-scapular arches do not join ventrally and are 

 attached to the inner sides of the clavicles. They present two 

 bony elements — the scapula and coracoid (by some regarded as 

 precoracoid) with persistent intervening cartilage. The scapula 

 usually has a foramen, and there is sometimes a third bony 

 element placed dorsal to the coracoid and in front of the scapula 

 and called the mesocoracoid. The clavicle (clei thrum) is a 

 large membrane bone meeting its fellow ventrally under the 

 throat. To its dorsal end there is usually attached a smaller 

 supraclavicle (supracleithrum) which is connected dorsally with 

 a forked bone the post- temporal. This bone is attached to the 

 auditory region of the skull, by one prong to the epiotic and 

 by the other to the pterotic bone. Projecting back from the 



* The pelvic paired fins are usually called ventrals. 



■'\ Cnlled cleithra by some anatomists, on the view that they are not 

 homologous with the clavicles of higher Vertebrates (see notes, p. 162). 



