Clas.sijication of the Order Salmopercce. 



2dl 



inuciferous channels on the upper surface of the head are 

 separated in the interorbital region by a median ridge or pair 

 of ridges formed by the frontals and continued forward ou 

 the mesethnioid ; on the snout the rnuciferous channels lie in 

 the large thin nasal bones, which are concave, with both outer 

 and inner edges raised, the latter nearly or quite meeting 

 above the ethmoidal ridge. The parietals are separated by 

 the supraoccipital ; the otic bones are all well developed ; the 

 exoccipital condyles are contiguous ; there is a thin-walled 

 auditory bulla formed mainly by thebasioccipital, exoccipital, 

 and pro-otic ; there is no basisphenoid, and the pro-otics do not 

 form a roof for the myodome ; the alisphenoids do not meet 

 in the middle line, and there is no orbitosphenoid. The pra2- 

 orbital and suboibitals are ossified, without subocular shelf; 

 there is no supraorbital ; the opercular and hyopalatine bones 

 are all present and normally developed; the palatine is 

 attached to the head of the vomer and has a maxillary 

 process; the prienuixillaries have short pedicels which lie 

 between the proximal ends of the maxillaries ; the latter are 

 broadest distally and have no supramaxillaries ; the lower 

 jaw is formed of dentary, articulare, and angulare. The lower 

 pharyngeals are coalescent by their inner edges ; there are 3 

 sepaiate dentigerous upper pharyngeals on each side. 



Vertebral column. — There are 30 to 36 vertebrae (13-17 + 

 17-19) ; the centra and arches are cc-ossified ; most of the 

 pra3caudals have rather strong transverse parapophyses ; the 

 ribs are strong, mostly inserted on the parapophyses ; the 

 epipleurals are feeble. 



A. B. 



CoJumhia irinmnontana . — A. Pelvic bones. B. Caudal fin skeleton. 

 ep, epurals (epaxial basalia) ; hy, hypurals ; c , last centrum ; %t, urostyle. 



Skeleton of caudal fin. — The caudal fin skeleton (fig. B) 

 shows one feature of generalization, in that the hypurals of 

 the upper and lower lobes are attached to separate centra; in 

 other characters it is highly specialized, for the hypurals are 

 few and the uroneurals are reduced, ankylosed with each 

 other and with the last centrum, forming a urostyle. 



