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 basibranchials {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 

 hones {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 

 «f'//''nN, \ 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. 



FlO. 112. — lliglit pertoral girrlle and fin o\T Gadiis 

 (after Gegenbaur). c clavicle (clcitliiiim) ; h 

 supraclavicle (supracleithrum) ; a post-temporal : 

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

 somactids of the fin ; h tony dermotricliia. 



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. 



+ Called cleithra by some anatomists, on the view that they are not 

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



