GEOLOGICAL SUEVEY OF THE TEREITOEIES. 475 



Color deep purplisli-brown, with ratlier scattered, irregular, yellow 

 spots with black margins ; rather paler below. 



From the Eio Grande, at San Jose, Costa Rica. Dr. Van Patten. 



This species, in general proportions, is a little more slender than the 

 last, but in general appearance, as size and coloration, can scarcely be 

 distinguished from it. It is a curious case of mimetic analogy. 



SiBOMA ATRAEiA, G., (TJ. S. Pac. E. E., Eep. X, 297.) 

 ' Abundant in Grass Creek, Idaho. Siboma differs from CUnostomus in 

 the anterior position of the dorsal fin. Collection Ko. 7. 



Myloleucus, Cope, gen. nov. 



Teeth raptorial, but with well-developed masticatory surface, 5-4 in 

 outer row. No barbels; lateral line well developed. Dorsal fin above 

 or in front of line of ventrals. 



This genus is Siboma, with developed grinding surfaces of the teeth. 



Myloleucus pulverulentus, Cope, sp. nov. 



Form stout; head short, muzzle not decurved; mouth terminal, 

 slightly descending, the maxillary bone nearly attaining the anterior 

 line of the orbit. Head 3.75 times in length, exclusive of caudal; depth 

 three and a half times. Eye 4.2 times in head, once in muzzle. Pre- 

 orbital bone deeper than long. Scales, 13-58-9. Eadii, D. I. 9 ; A. II. 7. 

 Caudal well forked. Length, 3^ inches. 



A dark plumbeous band extends from the origin of the lateral line 

 above to the caudal peduncle, and on it to the caudal fin. Below this 

 the color is silvery, thickly dusted with black dots; above it is an olive- 

 yellow band; then a dark dorsal region, all dusted. Sides of head sil- 

 very, dusted. Fins unspotted. 



Numerous specimens from the Warm Springs, Utah; type No. 6. 



Clinostomus pandora Cope, sp. nov. 



This species is nearly a Siboma, in consequence of the position of the 

 dorsal fin being so little removed from the vertical above the ventrals. 

 Dentition refers it to Clinostomus, while its appearance is that of a 

 Ceratichthys or Semotilus. I adhere to the technical characters until 

 others are found which will give us the clew to the truer affinities. 



Shape fusiform, head small, one-fifth of total length, (or fourth with- 

 out caudal fin,) broad, and rather flat at the muzzle. The latter does 

 not project, and the lips are equal. Maxilla not attaining the line of 

 the orbit by some distance. Eye small, 6.25 times in length of head, 

 twice interorbital width. Scales, 17-61-9, small in front of dorsal fin. 

 Eadii, D. I. 8; A. II. 8. Isthmus moderately wide; depth of body 4.2 

 times in length without caudal. Dorsal fin nearer basis caudal than end 

 of muzzle. 



General color silvery, above (in spirits) brownish. A broad, ill-defined, 

 lateral band, from epiclavicular region to basis of caudal fin, above the 

 lateral line. Length of type specimen, 8 inches. CollectionNo.il. 



From Sangre de Christo Pass, from a tributary of the Eio Grande. 



Clinostomus hydrophlox, Cope, sp. nov. 



This species and the folloAving are typical forms of the genus, and in- 

 teresting as the first that have been detected west of the Missis- 

 sippi Eiver. Length of head 4.75 times in total, exclusive of caudal 

 fin; depth of body 4.5 times in same. Eye 5 times in head, one and a 

 half times in interorbital width. Front straight; lower jaw projecting 



