690 Bulletin 4j, United States National Afuseum. 



317. ACROPCECILIA, Hilgendorf. 



Acropaccilia, Hilgendorf, Sitzuiigsberichte Naturf. Freunde, 1889, 52, (tridcns). 



Teeth in the inner series of '00th jaws trifid; otherwise essentially as 

 in I'acilia. Appearance of rwciUa, the dorsal very short, the mandible 

 weak, the dontary bones loosely articulated, the intestines with 4 con- 

 volutions. One species known, but very likely others now referred to 

 riicilia will be found to belong here, and the two genera may prove to 

 be inseparable, (a/c/jor, sharp ; Pwcilia.) 



1018. ACROP(ECILIA TBIDENS (Hilgendorf). 

 Head 4; depth 3; eye 3, 1| in interorbital space, '4 length of snout. 

 D. 7; A. 8; scales 27-9. Teeth in front row much elongate, band-like, 

 with broadened, truncate tips ; teeth of the 2 posterior series much smaller, 

 their cutting edge trifid, the middle lobe projecting beyond the others; 

 teeth similar in the 2 jaws; tips of all the teeth brown. Insertion 

 of dorsal in female a little farther from gill opening than from con- 

 vexity of caudal, the distance equal in males; dorsal somewhat behind 

 anal in females, much behind in males; dorsal higher than body in 

 males, half as high in females; pectoral 11- in head; lower jaw little 

 projecting. Coloration olivaceoTis, with black dots everywhere except 

 on belly and ventrals; a black network surrounding the scales, finest 

 on the tail ; young with distinct dark cross bands, and a dark vertebral 

 streak; opercle black ; a basal band on the dorsal; in the young and 

 the female a large black spot on j)08terior margin of the fin ; caudal 

 rarely with traces of vertical bands ; belly dirty silvery. Length 2 

 inches; male li inches. Port au Prince, Haiti. (Hilgendorf.) (tridcns, 

 three-toothed.) 

 PaciUa (Acropoecilia) tridcns, Hilgendorf, Sitzgsber. Natiirf. Frouiido, 1889, 52, Port au Prince. 



318. PCECILIA, Bloch & Schneider. 



Pircilia, Bloch & Schneider, Systema Iclitlij-ologia, 452, 1801, (viripara). 

 lAiiiin, PoEV, Meniorias, i, 388, 1855, [cnhenali). 



Body oblong, often rather deep; mouth small, transverse, with weak 

 jaws ; teeth small, in narrow bands, the outer series in each jaw being 

 usnally enlarged, curved, movable, and with brown tips; lower jaw not 

 prominent, its bones movable. Scales large. Dorsal fin rather small, of 

 7 to 11 rays ; anal fin short, in female nearly opposite dorsal in males 

 advanced and modified into a sword-shaped intromittent organ. Verte- 

 br;e about 28. Intestine long. Species mud-eating and viviparous. 

 This genus differs from Mollienesia only in the smaller size of tlie dorsal, 

 which has usually 9 or 10 rays and is nearly opposite the anal in the 

 female, but behind it in the male. The numerous species inhabit the 

 West Indies, Mexico, and South America. They are not well known and, 

 having never been critically compared, it is impossible to form an 

 analytical key to them on the basis of our present knowledge. Some of 

 them may prove to belong to Seterandria , and others to AcropwcUia, or to 

 other groui)8. {tzolkHoq, variegated, but the species are duller in color 

 than are those of related genera.) 



