FISHES CYPEIN1DAE GATOSTOMUS. 



223 



3. ACOMUS LACTABIUS, Grd. 

 PLATE L. 



SPEC. CHAR. Head constituting somewhat less than the fifth of the total length. Mouth small ; lips well developed, covered 

 with uniform granules. Eye large, sub-circular ; its diameter entering five times in the length of the side of the head. Anterior 

 margin of dorsal fin somewhat nearer the insertion of the caudal than the extremity of the snout. Insertion of ventrals situated 

 opposite the posterior half of the dorsal ; their tip extending to the vent. Greyish brown above; greyish white beneath. 



SYN. Catostomus (Acomus) lactarius, GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 174. 



it is closely allied to the preceding species, from which it differs hy a stouter head, larger 

 eyes, and larger scales on the body. The scales are longer than deep, sub-quadrangularly 

 elliptical, with radiating furrows upon their anterior and posterior sections alone ; a trait of 

 structure by which they may readily be distinguished from those of the preceding species. The 

 upper margin of the dorsal fin is concave, whilst it is nearly straight in A. griseus. 



D 13 ; A 10 ; C 4, 1, 8, 8, ], 5 ; V 11 ; P 17. 



The color is greyish brown above, and greyish white beneath. The fins being greyish olive. 



References to the figures. Plate L, fig. 1, represents Acomus lactarius, size of life. Fig. 2, a 

 scale from the dorsal region. Fig. 3, a scale from the lateral line. Fig. 4, a scale from the 

 abdominal region. Fig. 5, the young of the same species. 



List of specimens. 



CATOSTOMUS, Lesu. 



GEN. CHAR Head moderately elongated. Lips papillated ; lower one deeply cleft. The dorsal fin is generally longer than 

 high, and the size of the scales nearly equal anteriorly and posteriorly. The pharyngeals are provided with a little expansion 

 inferiorly ; the teeth being compressed, with the inner projection of the crown alone developed. 



SYN. Catostomus, LESU. in Jour. Acad. Nat. Sc. Philad. I, 1817, 89. RAFJN. Ichth. Ohiens. 1820, 53. Cuv. Regn. Anim. 

 2d ed. 11,1829; &, ed. illustr. Poiss. 220. STORER, Rep. Fish. Mass. 1839,83; Synops. 1846, 166 ; &, 

 Hist.^Fish Mass, in Mem. Amer. Acad. New S. V, 1855, 290. DEKAY, N. Y. Faun. IV, 1842, 196. HECK. 

 in Russeg. Reisen, I, ,1842, 1022. Cuv. & VAL. Hist. nat. Pois. XVII, 1844, 418. AGASS. Lake Sup. 1850 

 356; &amp;lt;K, m Amer. Journ. Sc. 2d ser- XIX, 1855, 92. GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 174. 



As characterized above, this genus contains yet numerous species, and, what is very curious, 

 it includes several species from the western slope of the Kocky mountains/together with those 

 originally known in the eastern States. 



