16. I'CECILIA. 341 



d-rj. Females, 3^ inches long. lUver Chisoy, Vera Paz. From 



Mr. Sahdn's Collection. 

 h. Manj- specimens, females, 2-3 inches long. Lake of Amatitlan. 



From Mr. Salvin's Collection. 

 i. Many specimens, 1-2| inches long, mostly females, and thi-ee males. 



Lake of Amatitlan. From Mr. Salvin's Collection. 



4. Poecilia thermalis. 



Poecilia thermalis, Steindachm-, Sitzgsher. Akad. Wiss. Wien, 1863, 



xlviii. p. 181, taf. 4. figs. 3, 3 a. 

 PGambusia (?)modesta, Troschel, in jiiiller's Eds. Mex. iii. p. 105. 

 Yery closely allied to P. dovii, but with a broader head, with the 

 body more elongate, &c. 



D. 9-10. A. 8-9. L. 30. L. transv. 9. 



The height of the body (measni-ed between the origins of the dorsal 

 and anal fins) is contained thrice and three-fourths in the total length 

 (without caudal), and equals the length of the head ; the width of 

 the interorbital space equals the distance between the front margin 

 of the orbit and the giU-opening. The diameter of the eye is a little 

 more than the length of the snout, contained thrice and one-third in 

 that of the head, and a Uttle more than one-half of the interorbital 

 space. The origin of the dorsal fin is midway between the root of 

 the caudal and the occiput, and corresponds to the twelfth scale of 

 the lateral line. Origin of the anal opposite to the third ray of the 

 dorsal in the female. Dorsal fin of moderate size, anal smaU ; caudal 

 scaly at the base only. Tail compressed, moderately elongate, its 

 least depth being somewhat less than the length of the head, mth- 

 out snout. There are seven longitudinal series of scales on each side 

 of the tail. Lateral line rather distinct. Greenish, a faint darker 

 streak along each series of scales ; frequently a round blackish spot 

 in the middle of the side in females. 



The male has the dorsal fin elevated, and the longest ray is at least 

 as long as the head, without snout ; this fin is ornamented with large, 

 ovate black spots, occupying the lower half of the fin, and sometimes 

 confluent into one large 2)atch. Anal fiji modified into an intromittent 

 organ, and advanced to between the ventrals and in front of the 

 dorsal. Tail strongly compressed, and comparatively rather higher 

 than in the female. Interradial membrane of the caudal fin vnth 

 oblong black spots, nothing of which is visible in the female. 



Central America. 



a. Females, from ] | to 24 inches long. San Salvador, warm springs. 



Presented by Capt. Dow. 



b. Males, 2 inches long. Presented by Capt. Dow. 



Prof. Troschel informs me that his Gamhiisia {?)modesta ought to 

 be referred to Pcecilia as characterized above ; but it is not quite cer- 

 tain whether it is specifically identical with P. thermalis. 



