402 EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



POTAMOCOTTUS PUNCTULATUS, Gill. 



The general form of the body is similar to that of the first division of the first sec- 

 tion of (Jirard's Cot ft. It is elongated, slender, and considerably compressed. Of the 

 extreme length, tin- head forms throe-tenths parts and the caudal fin between a fifth 

 and sixth. The trunk is anteriorly cylindrical, the height being scarcely more than 

 the width behind the pectoral fins. The greatest height is at the commencement of 

 the iirst dorsul fin, and exceeds a seventh of the extreme length; from thence, the 

 height declines gradually to the caudal peduncle, where it is only equal to a third of 

 the greatest The breadth also declines uniformly, but more sensibly, to the base of 



The head is much depressed, and rhomboidal-ovate above. From the snout to 

 the membraneous margin of the operculum, it forms a third of the entirel ength. Its 

 breadth is very great and is only about a sixth less than its length. The height at the 

 occiput is about a half of the length. The snout is anteriorly broadly rounded. 



The mouth is quite large; the jaws arched and receding; the distances between 

 the extremities of the mamillaries being equal to the length of the caudal fin. The max- 

 illary terminates under the anterior margin of the pupil. The upper jaw is somewhat 



The jaws are armed with bands of small, recurved, acute teeth; those on the den- 

 taries are somewhat shorter than those of the premaxillaries, and reach much farther 

 backward, extending to the angles of the mouth; the band is narrow as it recedes 

 backward At the symphysis of each jaw, there is a narrow interval, separating the 

 bands into two equal parts. The chevron of the vomer and the palatines are also 

 armed with bands of villiform teeth; those on the latter bones are perfectly evident, - 

 and almost as large as those of the vomer; they are in bands which are narrowed pos- 

 teriorly. 



The eyes are of the usual size, and situated about midway between the snout and 

 the margin of the preoperculum. The width of the frontal bones between the eyes is 

 about equal to the diameter of the orbit. 



The preopercular spine is stout and directed obliquelv backward and upward. 

 The one below is small and pointed downward. On the inferior margin is another still 

 smaller. The subopercular spine is moderate, acute, and directed forward. 



The breadth of the isthmus separating the branchial apertures is equal to five- 

 ninths of the length of the caudal fin. The branchiostegal bones are of the normal 

 number of six. 



The first dorsal lias eight rays: the last is connected by a membrane decreasing 

 in height to the second dorsal, where it is extremely low. 



The anal fin has about the height of the second dorsal, and commences under its 

 third ray. 



The caudal forms between a fifth and sixth of the entire length. Its posterior 

 margin, when fully expanded, is rounded; most of its rays are doubly bifurcated. 



The pectorals extend backward to about the vertical of the sixth ray of the second 

 dorsal; all of their rays are simple. 



