NATURAL SCIENCES OF PHILADELPHIA. 121 



LVI. As to Gambusia pa'ruelis, numerous specimens of that species were col- 

 lected in the upper affluents of the Rio Nueces, by Dr. C. B. R. Kennerly, under 

 Capt. A. W. Whipple, during the Exploration near the thirty-fifth parallel, for 

 a railroad route to the Pacific. The average size of either sex corresponds 

 pretty nearly to the specimens figured on plate xxxix, of the "Ichthyology of 

 the U. S. and Mex. Boundary." Specimens from the Rio Leona, Rio Blanco, 

 and Rio Seco, exhibit a somewhat lighter tint than those from the lower part 

 of the same hydrographic basin. But this may be an alteration subsequent to 

 their immersion in alcohol. 



LVII. A curious little species of Gambusia from the hydrographic basin of the 

 Rio San Juan, specimens of which having been collected in Rio San Diego, one 

 of its affluents, near Cadereita, New Leon, by D. N. Couch. The largest ones 

 measure an inch and a half in total length, and belong to the female sex alone. 

 The body is deep upon its middle and the tail tapering. The head enters about 

 four times and a half in the total length. The eye is proportionally large and 

 circular ; its diameter entering three times in the length of the side of the head. 

 The dorsal fin is very narrow and elevated, and proportionally higher than 

 in the other species so far known of this genus. The anal fin is likewise nar- 

 row and deep, and resembles the dorsal in that respect. The ventrals are 

 small, and the pectorals well developed. We have not been able to count with 

 accuracy the rays of the fins, owing to the desiccated condition of the specimens 

 preserved ; in the dorsal and anal fins they are less numerous than in the 

 other species of the genus. The color of the body is reddish-brown, except 

 the belly, which is yellowish or whitish. Small black spots may be observed 

 along the dorsal region near the base of the scales. The dorsal and anal fins 

 are greyish ; the caudal ventrals and pectorals, olivaceous. 



The species might be designated under the appellation of Gambusia speciosa. 



LVIII. In the collection of the late Louis Berlandier, of Matamoras, we find 

 another species of Gambusia, which differs from its congeners by the slender- 

 ness of its form and general appearance : hence the name of G. gracilis by 

 which we propose to record it. 



The largest female specimens measure about an inch and a half in total 

 length, of which the head constitutes a little more than the fifth. The mouth 

 is rather large compared to that of the foregoing species. The diameter of the 

 eye enters about three times in the length of the side of the head. The body 

 in its profile is subfusiform. The dorsal fin is higher than long, superiorly 

 convex. The caudal is rounded off posteriorly. The anal is larger than the 

 dorsal, deeper than long and exteriorly convex, the posterior extremity of its 

 insertion being nearly opposite the anterior margin of the dorsal. The tip of 

 the ventrals extends almost to the anterior margin of the anal. The pectorals 

 are well developed and project beyond the insertion of the ventrals. The rays 

 are : D 6 ; A 9 ; C 5, 1, 6, 6, 1, 4 ; V 6 ; P 13. The scales are moderate sized, 

 much deeper than long, subelliptical in their outline, more convex posteriorly 

 than anteriorly with numerous and well developed radiating furrows upon the 

 anterior portion alone. 



The largest male specimens which have come under our observation mea- 

 sure a little over an inch in total length. They are very similar to the female 

 sex, rather more slender. The anal fin exhibits the usual structure peculiar 

 to that genus. The first ray is a mere rudiment ; the second being the stoutest 

 and longest ; the third forms, with the second, the elongation of that fin, and 

 is followed by four shorter rays somewhat better developed, however, than in 

 the other species, which we have examined. 



The color is olivaceous brown ; the dorsal and caudal fin exhibits narrow 

 transverse, blackish bars ; the other fins being olivaceous. 



LIX. Mr. John Potts has collected in Chihuahua River another species of Gam- 

 busia which appears to reach a larger size than any of the foregoing spe- 



1859.] 



