1854.] 125 



and ventrals ; scales medium size ; lateral line nearly concurrent with the back ; 

 intestinal canal short; eyes very large, irides white, with a brown crescent 

 above. 



H. argenteus. Back regularly arched with a slight incurvation along tbe 

 frontal bone; curve of the belly greater than that of The back ; upp?r lip on a 

 line with the superior edge of the orbit; sides of the upper jaw nearly vertical ; 

 lower jaw the longer ; dorsal has eiuh r to nine spinous rays, 1st short ; 2d, 3d 

 and 4th, double the length of its preceding one, the 6th ray being the longest ; 

 dorsal groove obsolete along the soft rays; pectorals cuneiform, first one short 

 and spinous; first three rays of anal tin spinous ; a space quarter of an inch wide 

 free of scales extends from the base of the ventrals round the vaginal orifice; 

 nostrils double, anterior ones closed with a valve ; two or three rows of very fine 

 scales along the base of the anterior third of the anal ; scales above the lateral 

 line, and round the fins smaller than elsewhere ; head ash color and dark brown ; 

 back light brown with blue metallic tints, silver white beloiv the lateral line ; 

 from 22 to 24 silver white longitudinal stripes ; outer edge of dorsal membrane, 

 caudal and ventrals, darkly punctated, tips of ventrals black. Length including 

 tail, 9 inches; width 4.5 inch ; weight half pound. 



D. 35 ; P. 26 to 28 ; V. 6 ; A. -36 to 40 ; C. 22. 



H. arcuatus, Gibbons. Curvature of the dorsum greater, and of the belly lest 

 than of the Argenteus. Mouth lower, in reference to the eyes. Head shorter, 

 eyes smaller, dorsal groove longer. About the same size as the other. 



Micrometrus, Gibbons. 



Head of medium size, body ovate, compressed ; snout protractile ; lips thin; 

 cheeks and opercula scaly ; teeth conical, in a double row in each jaw, the inner 

 row having from four to six ; branchiostegal rays five ; dorsal commences behind 

 the pectoral, and about opposite the ventrals; scales rather large; intestinal 

 canal six to ten inches long ; eyes of medium size ; tail forked. 



M. aggregatus, Gibbons. Back slightly arched; lateral linenot concurrent 

 with the dorsal outline; belly curved more than the dorsum; space behind the 

 ventrals covered with scales; head ash color; body with eight or nine longitu- 

 dinal rows of black spots, commencing below the lateral line and becoming 

 obsolete opposite the end of the dorsal, which are interrupted by three or four 

 lemon colored vertical bands; back dark brown, with blue metallic tints; belly 

 and tail silver white; extreme length five inches; width, including the dorsal, 

 2.25 inches ; weight two ounces. 



D. 21 ; P. 20 to 24; V. 6; A. 16; C. 20. 



M. minimus. Dorsum more curved than the preceding; back brown with 

 metallic blue tints, sides punctate with black, with lemon color patches alom* - 

 the middle; a diffused dark brown or black spot about the end of the spinous 

 rays ; membrane of the dorsal, of the tail and anal punctated black, ventrals 

 yellow at base, tipped with black: a diffused black patch under the pectorals. 

 About the same size as the preceding. 



Var. a. All the characteristics of the preceding, but with larger scales and 

 lighter color; extreme length six inches; width 3.25 inches. 



My i'ilophagus, Gibbons. 



Head of medium size ; snout slightly protractile; lips thickened ; cheeks and 

 opercula covered with scales: with a soft membrane around the ed<es ; body 

 oblong ovate, subcompressed, arched; back somewhat flattened; teeth conical 

 a double row in each jaw, those of the lower jaw extending to the an^le of the 

 mouth; branchiostegal rays six ; pectorals anterior to the dorsal; lateral line 

 nearly concurrent with the back; scales large. 



M. fasciatus, Gibbons. Curvature of belly greater than that of the back ; 

 eyes rather large, about a quarter inch above the line of the upper lip ; lower 

 jaw a little the 'oiger ; dorsal with ten spinous rays, first short, the succeeding 

 ones gradually in:reasing in length to the sixth, which is the longest, being 



