Jordan and Evermann. Fishes of North America. 701 



with scales at base only. Free portion of the tail as high as long, and 

 covered by 9 longitudinal series of scales on each side. Brownish green, 

 silvery below ; a dark spot 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 cau- 

 dal 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. Length 5 inches. Lake Peten. 

 (Giinther.) Extremely close to M. latipinna, but reaching a larger size, 

 its angulated caudal suggesting Xiphophorus. 



?,Iollien?*ia j>ct<>>te>isig, GVNTHER, Cat., vi, 348, 18C6, Lake Peten, in Guatemala. (Coll. Salvin.) 



320. XIPHOPHORUS, Heckel. 



Xiphophorus, HECKEL, Sitzgsber. Akad. Wise. Wien, 1848, i, pt. 3, 163, (helleri). 



This genus differs from Mollienisia only in the structure of its caudal 

 fin, the lower rays of which in the males are prolonged into a long sword- 

 shaped appendage, which in the adult is sometimes as long as the rest of 

 the fish. Anal of the male modified into an intromittent organ, 1 or 2 

 of the enlarged rays being provided with hook-like processes. Branchi- 

 ostegals 5. Vertebrae 16 -{- 14 = 30. (?70of, sword; 0opw, to bear.) 



u. Sides in both sexes with dark lines of spots along the rows of scales; a darker stripe ou side 



running along upper edge of caudal projection. HELLERI, 1042. 



aa. Sides in both sexes covered with irregular black blotches and spots, not following the rows 



of scales; no lateral stripe. OUNTHERI, 1043. 



1042. XIPHOPHORUS HELLERI, Heckel. 



Head 4fr ; depth 3 to 3*. D. 13; A. 9 ; V. 6; scales 29-8. Eye as long 

 as snout, 3i in head. Dorsal nearly equal in males and females, its base 

 3 in distance from head to caudal; caudal sword in adult male nearly 

 as long as the fish, yellow, with black edges ; ventrals below front of 

 dorsal in both sexes. Body in female with regular series of dark spots 

 forming lines along the TOWS of scales as in Mollienisia', dorsal plain 

 in the female, spotted in the male, the spots in horizontal rows. Rivers 

 of southern Mexico and Central America. Giinther describes three varie- 

 ties in the coloration of males ; variations possibly representing distinct 

 species : 



a. Two yellowish-green bands along side, separated and bordered above 

 and below by a blue band. Rio Chisoy. 



&. Middle blue band darkest, black, running from eye to and along 

 upper border of caudal appendage, which is very short. Cordova. 



c. Body without bands, covered all over with irregular black spots in 

 both sexes. Rio Chisoy. This form (figured by Giinther, Fish. Centr. 

 Amer., 1869, pi. 87) we have here regarded as a distinct species, Xipho- 

 phorus guntheri. 



(Named for Prof. Karl Heller.) 



Xiphophorus helleri, HECKEL, Sitzgber. Akad. Wise. Wien, 1848, i, 163 ; GCNTHER, Cat., vi, 349, 

 1866; GtJNTHER, Fishes Centr. Amer., 485, 1869. 



