CYPR1N1F0RMES 377 



is also remarkable for the possession of a large number of pectoral radials 

 (8), like Anguilla (Sagemehl [379] and Fig. 363). 



Fig. 303. 



1; urn not us electricus, L., dissected so as to show the electric organs on the right side, k 

 and '?; h, reflected body-wall. (From Owen, Anatomy of Vertebrates, by permission of 

 Messrs. Longmans and Co.) 



Gymnotus, Cuv. ; Campus, M. and T. ; Stemopygus, M. and T. ; 

 Sternarch'us, Cuv. ; Rhamphichthys, M. and T. — S. America. 



Tribe B. Siluroidei. 



Normal Teleostean scales are never present, the body being either naked 

 or covered with overlapping plates, or armed with a stiff cuirass. Possibly 

 both these are modified scales (Fig. 373). On the head and shoulder 

 region the dermal skeleton is usually very well developed ; the bones 

 being generally ornamented, close-fitting, and expanded so as to form a 

 cephalic shield, in which may become involved the post-temporal and 

 supraclavicle (Fig. 366). The cleithrum may also develop a large dermal 

 plate. The postclavicle is absent. There is no eye-muscle canal ; and 

 no distinct parictals, these bones being probably fused with the supra- 

 occipital, formed by the combination of a large dermal plate with an 

 endochondral element (unless the parietals are represented by two small 

 supratemporal bones pushed outwards and backwards). Only one ptery- 

 goid persists ; there is no symplectic bone, and the palatine is toothless, 

 often rod-like, and sometimes vestigial. The subopercular has the 

 appearance of a branchiostegal ray, and the maxilla generally becomes 

 converted into a small ossicle supporting the cartilaginous axis of the 

 barbel (Figs. 364, 366, 367). The premaxilla, dentary, vomer, and 

 generally the pterygoid, are toothed [252, 274, 286, 290, 332, 410]. 



The anterior vertebrae are more modified than in the Characinidae. 

 A complex vertebra, behind the small first centrum, is made up of three, 

 four, or even five centra, forming a single mass which may be co-ossified 

 with the first centrum and the basioccipital. The parapophyses are long, 

 especially in front, and those of the fourth, and sometimes also of the 

 fifth vertebra, are immensely enlarged and project outwards to articulate 

 with the massive post-temporal (Fig. 367). The latter has one limb 

 articulating with the basioccipital, and another with the epi- and pterotic. 

 The enlarged parapophyses more or less, thoroughly invest the anterior 

 chamber of the air-bladder, sometimes in a complete bony capsule [58]. 



The air-bladder is typically subdivided internally into an anterior 

 transverse chamber and paired posterior chambers. In many cases it 

 undergoes degenerative changes, becoming very small and almost solid, the 



