17. MOLLIENESIA. 349 



one-half of the distance between eye and root of the caudal, in the 

 female two-fifths ; caudal rounded, with scales at the base only. 

 The free portion of the tail is as high as long, and covered by nine 

 longitudinal series of scales on each side. Lateral line veiy indis- 

 tinct. Greenish, or brownish green, silvery below ; a dark sjiot to 

 each scale of the upper and middle caudal series and the lower part 

 of the trunk. Dorsal fin of the adult male with small irregular 

 brown lines or spots, and with a row of large rounded spots along 

 the middle of its height. Interradial membrane of the caudal with 

 numerous black dots ; the lower part of the hind margin black. 

 Females and immature males have the dorsal fin simply ornamented 

 "with small irregularly curved brown spots. 

 Lake Peten. 



a, h. Several male specimens (from 4 to 5 inches long) and one 



female, (4| inches long). From Mr. Salvin's Collection. 

 c. Adult male : skeleton. From Mr. Salvin's Collection. 



Although this species is very closely allied to M. lutipimm, it is 

 evidently chstinct, having constantly fifteen dorsal rays and a dif- 

 ferent coloration. 



3. Mollienesia formosa. 



Limia formosa, Girard, Proc. Acad. Nat. Sc. PMlad. 1859, p. 115. 

 D. 12-13. A. 10. 



Male. The height of the body is nearly equal to the length of the 

 head, which is one-fourth of the total (with the caudal) ; the dia- 

 meter of the eye is one-third of the length of the head ; snout ab- 

 breviated. Dorsal fin longer than high ; anal fin nearly opposite 

 the anterior margin of the dorsal ; ventrals in advance of dorsal. 



Female. Dorsal fin nearly as high as long, with the anterior 

 margin somewhat nearer the root of the caudal than the extremity 

 of the snoiit. Anal fin opposite the posterior portion of the dorsal. 

 Pectoral extending beyond the origin of the ventral. 



Dorsal fin with transverse series of blackish spots, the other fins 

 immaculate. (Glr.) 



Paolo Alto (Mexico). 



^. XipIiojjJiorus. 

 1. Xiphophorus hellerii. 



Xipliophorus hellerii, Heckel, Sitzgsher. Akad. Wiss. Wien, 1848, i. 

 part .3. p. 163, pi. .5 (male, young male, and female). 



B. 5. D. 13. A. 9. V. 6. L. lat. 29. L. transv. 8. Vert. 16/14. 

 The height of the body is contained from thrice and one-half to 

 thrice and four-fiftlis in the total length (without caudal), the 

 length of the head four times and one-third. The diameter of the 

 eye is equal to the length of the snout, and two-sevenths of that of 

 the head ; in males it is scarcely equal to one-half of the width of 

 the interorbital space, whUst it is somewhat less in females. Dorsal 

 fin in males and females of nearly equal length, viz. two-sevenths 

 of the distance between head and caudal fins ; it is somewhat ale- 



