974 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. xxviir. 



The principal difierences from the previously recognized form of 

 trfdrnfatus are the posterior origin of the lirst dorsal, the absence of 

 any interval l)etween the two dorsal tins, and the greater height of the 

 tins; there is also a distinct precaudal fold which extends forward to 

 the vent. The head is also longer, the eye larger, and the tail shorter. 



The arrangement of the teeth is wholly similar to that in oi'dinarv 

 tridentdtus. The supra-oral ]>late contains two large lateral and a 

 small median cusp, the latter distinct, but less than half the length of 

 the lateral cusps. The infra-oral plate is crescentic. with live equally- 

 spaced broadly triangular cusps. There are al)out three series of very 

 small simple teeth on tlie disk in front of the pre-oral plate, the 

 median tooth larger than the others. Behind the infra-oral lamina 

 are two series, one near the margin, the other halfway between the 

 luargin and the infra-oral lamina. The inner series consists of 16 

 small teeth, each inserted at the inner end of a short radial furrow. 

 The anterior tooth on each side is ))icuspid, all the others simple. The 

 lateral portion of the disk contains on each side four larger plates, 

 the anterior and posterior of which are bicuspid, the others ti'icuspid. 

 The anterior lingual plate has a straight transverse margin, very 

 finely pectinate. The mai'gin of the disk is densely fringed. 



The eye is large, its diameter ecpialing half the interorbital width. 



The front of the dorsal is behind the middle of the total length. 

 Its greatest height is two-tifths the length of the tin ]>ehind its origin. 

 Posteriorly, it joins the l)ase of the second dorsal, being abruptly 

 notched at point of union. The second dorsal is very high, its longest 

 rays, including nuiscular area at base, one-fourth the length of the 

 base. A vertical line from the vent traverses the second dorsal at the 

 end of its first fourth. In advance of the lower half of the caudal fin 

 a well-defined rayless fold of the integument extends forward to the 

 vent, increasing in height anteriorly and ending in a rounded lobe. 



In spirits, the color is slatv-brown, the posterior part of the first 

 dorsal and the anterior end of the anal fold white. The caudal fin is 

 largely black. The lips and gullet are slaty, the buccal disk Avhitish. 



Measitrements hi hun(lri'(lt]is of total lengtJi. 



Total length ( in millimeters) 



Length of snout 



Length of head to first gill slit 



Distance between first and last gill slits 



Diameter of eye 



Length before dorsal 



Base of first dorsal 



Interspace between dorsals 



Height of first dorsal 



Base of second dorsal 



Length of caudal from upper notch 



Distance from vent to tip of tail 



W^s'hiL-' ^o^"*' 

 ton ^'^'^''• 



350 



8.9 

 14 

 10.8 



2.3 

 'A 

 16 







2.6 

 23. 3 



6.5 



Male. 

 425 



9 



14.5 

 11 



2.3 

 51.5 

 1.5.5 







4.3 

 26.5 



8 

 26 



Klamath 

 River. 



Female. 

 263 

 8 



11.5 

 9.5 

 1.9 

 50 

 14 

 5.2 



24.5 



Rogue 

 River. 



535 



7.2 

 11.4 

 10.2 



1.4 

 49 

 15 



5 



2.5 

 25 



7 

 29.5 



Rogue 

 River. 



Sexf 

 580 



7.1 

 11 

 10.5 



1.5 

 46.5 

 17 



5 



2.3 

 24 



29^2 



