234 DR. A. GUNTHER ON NEW AMERICAN FISHES. [Mar. 26, 



ample, 22 inches long, at Xeberos. It has no adipose fin ; there- 

 fore Kner's assertion, that the absence of this fin in the typical ex- 

 ample is merely accidental, is not confirmed. 



Hypoptopoma (g. n. Hypostomatinum.). 



This genus differs from Plecostomus in the peculiar formation of 

 the head, which is depressed, spatulate, the eyes being on the lateral 

 edge of the head. The moveable gill-covers are reduced to two 

 bones, viz. the operculum, small and placed as in Plecostomus, and 

 a second, larger bone (interoperculum ?), separated from the eye by 

 the narrow suborbital ring, and placed at the lower side of the 

 head. 



Fig. 2. 



HypopfoTpoma thoraccduni. 



Hypoptopoma thoracatxjm. (Fig. 2.) 



D. 1/1. A. 6. P. 1/6. V. 1/5. L. lat. 24. 



The form of the head approaches that of Loricaria, being much 

 depressed ; the snout broad, with the outline elliptical. The inter- 

 orbital space is slightly convex, but little narrower than the greatest 

 width of the head, which is three-fourths of its length. The 



