NATURAL SCIENCES OF PHILADELPHIA. 119 



W. Rich, in 1853, we notice a cyprinodont of a very peculiar external appear- 

 ance, belonging nevertheless to the genus Lucania, as characterized above. 



One of the female specimens measures two inches and a half in total length. 

 The dorsal region is very much arched from the insertion of the dorsal fin to 

 the nape, which is quite swollen. The head is rather small, constituting the 

 fifth of the total length, its upper surface is subdepressed, the occipital region 

 appearing concave from the sudden rising of the nape, a trait less conspicuous 

 in smaller specimens of the same sex and in the males also. The snout is 

 short, thick and blunt. The gape of the mouth is oblique upwards as in the 

 other species of this genus. The eye is subcircular, its diameter entering 

 three times and a half in the length of the side of the head. There are three 

 slender branchiostegal rays on either side, the outermost being exiguous. 

 The anterior margin of the dorsal fin is nearly equidistant between the apex 

 of the snout and the posterior margin of the caudal fin ; its upper margin 

 is convex and its base is longer than the height of the middle rays. The 

 caudal fin enters a little short of seven times in the total length. The anal, 

 is smaller than the dorsal, but has the same shape, and the same propor- 

 tions between its base and its depth. Its anterior margin is placed poste- 

 riorly to that of the dorsal ; the tip of its rays extending but very slightly 

 further back than those of the latter, so that the two fins are nearly 

 even posteriorly. The ventrals are very small and reach the vent with their 

 extremities. The pectorals are of moderate development, rounded off, not ex- 

 tending as far as the origin of the ventrals. The rays are : D 20 ; A 23 ; C 5, 

 1, 10, 10, 1, 6 ; V 6 ; P 12. The scales are comparatively small, deeper than 

 long, snbelliptical in their outline, exhibiting extremely fine concentric lines of 

 growth, and provided with radiating furrows upon their anterior section alone. 

 The ground color is olivaceous brown, with transverse dark brown bands which 

 run occasionally together giving the entire body, head and fins, a greyish black 

 appearance. Otherwise the fins assume a greyish olive tint. 



The male sex is more slender than the female ; the dorsal and anal fins being 

 somewhat more developed, and the back less arched. The coloration is similar 

 in either sex. 



LII. In speaking of the generical characters to be assigned to Girardinus, 

 and especially of the structure of the mouth, we ought to have stated that the 

 latter is depressed, instead of being rounded, and constructed after the fashion 

 of that of Pacilia and Limia, so that its gape is directed upwards when con- 

 tracted, and downwards when protracted. Accordingly its affinities with the 

 latter two genera are more intimate than with Gambusia. 



The specimen of Girardinus occidentalis, figured, size of life, on plate xxxix, 

 of the " Ichthyology of the U. S. and Mex. Boundary," is the largest of those 

 collected in the Rio Santa Crux, by John H. Clark, under Col. J. D. Graham. 

 Specimens two inches and a quarter in total length were subsequently collected 

 at Tuczon, Sonora, by Arthur Schott, under Major Emory. All these speci- 

 mens belong to the female sex. The following formula of the fins is to super- 

 sede that which has been previously published : D 7 ; A 7 ; C 4, 1, 7, 7, 1, 3 : 

 V 6 ; P 12. The scales are subelliptical, deeper than long, with radiating fur- 

 rows upon the anterior section alone. The ground color is either reddish or 

 olivaceous brown above, and yellowish white beneath, with a golden reflect 

 during the breeding season. The periphery of the scales exhibits blackish dots 

 occasionally so crowded as to assume a dark appearance. Along the middle 

 of the flanks may be seen a black fillet which imitates a lateral line ; the series 

 of scales over which it runs is sometimes entirely black. A black streak is 

 observed along the under edge of the peduncle of the tail. The fins are of a 

 uniform light yellowish tint. 



We refer, for the present, to the same species, numerous specimens in a 

 rather indifferent state of preservation, collected at Tuczon, by Dr. A. L. H er- 

 mann, under Lt. J. G. Parke. Amongst them we observe several individuals 

 1859.] 



