TELEOSTOMOUS FISHES. 



245 



("clavicle of authors), the cleithra of the two sides frequently 

 uniting below. Other smaller membrane bones, some of them 

 less constant, are the supra-, post-, and infraclavicles ; and the 

 arch is usually articulated to the otic region of the skull, either 

 by the supraclavicle, or by the intervention of a post-temporal 

 bone between the supraclavicle and the epiotic. The pelvic 

 arch is either greatly reduced (ganoids) or entirely absent 

 fteleosts), its place being supplied by the greatly enlarged 



FIG. 246. Skull of perch. B, basalia of fin ; C, coracoid ; CL, cleithrum ; IO, 

 infraopercular ; J/, maxillary ; 0, opercular ; PC, postclavicula ; PO, preopercular ; 

 /'J/, premaxilla; PT, post-temporal; Q, quadrate; K, radialia of fin; .SO, sub- 

 ocular chain of bones, also suboperculum ; S, scapula. 



basalia (see, however, p. 173). The dorsal and anal fins are sup- 

 ported upon small interspinous bones embedded in the flesh and 

 usually alternating with the neural and haemal spines, or they 

 may be more numerous than these. The caudal fin is either 

 heterocercal, or the lower lobe may be so well developed that 

 the homocercal condition occurs (p. 229). The ribs, except in 

 Polyptcrns, where both types occur (p. 145), are modified haemal 

 arches ; and the flesh is further supported by intermuscular 



