400 EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



I am able to say, from an examination of the specimens used ])y Dr. Girard liimself 

 for description, that it agrees witli all allied species in having- the normal number of 

 seven, which are developed as in Moronc amcricana. 



There are preserved in the nniseum of the Smithsonian Institution three speci- 

 mens of the 3forone interrapta, one of which was obtained by Lieutenant Couch at 

 New Orleans, and two larger ones were found at Saint Louis, Mo., by Dr. George 

 Engelmann. The small specimen from New Orleans dift'ers from the two Missouri 

 specimens by the larger second spine of the anal fin, but in ever)' other respect they 

 are similar. 



Family COTTOID^, (Rich). 



Subfamily COTTINyE, (Bon.). 



Genus POTAMOCOT^fUS, Gill. 

 Synonymy. 



PoTASiocoTTUS Gill, Pioc. Bostou Soc. Nat. Hist. 



COTTUS sp. Agassiz, Lake Superior, &c. 



CoTTUs sp. Giraid, " Mouograph of the Cottoids of North America " in Smithsonian Contributions to Knowledge, vol. iii. 



Body elongated, anteriorly subcylindrical, and thence declining in height toward 

 the caudal, where it is also much compressed. Tlie skin is perfectly smooth and 

 naked, except sides behind the pectorals. 



Head conical or cuneiform in profile, oval above and depressed, and covered by a 

 naked skin. The jjreoperciilum is armed at its posterior margin with a strong spine, 

 curved upward, and below with one or two smaller ones, or tubercles; the antero- 

 inferior angle of the sub-operculum is also armed witli a spine directed forward and 

 downward. The other bones are unarmed. 



JEyes mostly situated in tJie anterior half of the head; frontal bones between them 

 of moderate width. 



Mouth slightly oblique, and its gape is quite large. 



Tceih villiform on the jaws and V(^mer as well as palatine bones. 



Branchial apertures vertical and oblique, entirely separated from each other b}' a 

 perfect isthmus, as wide or wider than the interval between the bases of the ventrals. 

 There are six l)ranchiostegal rays. 



Dorsal fins two, either entirely separate or connected by a low membrane. The 

 first has from six to nine slender spines. 



Pectorals rounded, and their rays generalh- unbranched. 



Ventrals nearly under the pectorals, and have a spinous and four (rarely three) 

 unbranched rays. 



The genus Potamocottus in every respect resemldes the Urtiiridea, except in the 

 presence of a band of villiform teeth on each palatine bone. Several species properly 

 referable to this subgenus have been described as true Cotti. It is equally closely 

 related to the genus Cottopsis of Girard, but is distinguished by its smooth skin. The 

 s})ecies named by Girard Cottopsis yidosus is a true Pottamocottus. 



The propriety of retaining the species with palatine teeth in the genus Cottus 



