FiSHUs OP THE Order Cyprinodontes 17 



IV. The Subspecies oe Pseudoxiphophorus bimacueatus 



AND OF PrIAPICHTHYS ANNECTENS 



I 



Two species of cyprinodont fishes from Middle America exhibit geograph- 

 ical variation sufficiently well defined and extensive as to require division 

 into subspecies. These species are PseiidoxiphopJiorus biinaculatus of south- 

 ern Mexico and Guatemala, and PriapicJifhys ainicctciis of Costa Rica. 



II 

 PseudoxipJiopIionis biinaculatus Meckel 



This species, which inhabits the Atlantic drainage from central Mexico to 

 Guatemala, comprises a complex of races distinguished only by average, 

 intergrading characters. Provisionally it may be divided into three subspe- 

 cies, two of which have been regarded as distinct species. Of these sub- 

 species, the typical bimaciilatiis is intermediate, the two extreme subspecies 

 being P. b. taeniatus Regan and P. b. jonesii Giinther. These subspecies 

 form a series grading from jonesii of the higher mountain streams and lakes 

 of east-central Mexico through the intermediate biinaculatus of the lower 

 and somewhat warmer waters back of Vera Cruz into the more southern form. 



The characters which distinguish these suljspecies are those of form and 

 proportions, color, and, particularly, the number of dorsal rays. From 

 extreme taeniatus to jonesii, that is, toward the north and toward higher ele- 

 vations, the body becomes deeper, the head longer, the color paler, the dorsal 

 rays reduced in number. The difference in the numl)er of dorsal rays is 

 summarized in the following table : 



Frequency tabic. — Number of dorsal rays in ilic three subspecies of Pseudo.vipho- 

 phorus biinaculatus: 



— Number of dorsal rays • 



II 12 13 14 15 16 17 



P. b. jonesii 15 5i 9 6 3 



P. b. bimaculatus i 29 21 3 



P. b. taeniatus''- .... 7 13 4 i 



The correlations of these variational phenomena will I)e considered by the 

 writer in a subsequent paper. 



Pseudoxiphophorus biinaculatus jonesii Giinther 



Motlicnisia jonesii Giinther, Ann. Mag. Nat. Hist., (4) 14, 1874, p. 371 ; Garman, 

 Mem. Mus. Comp. Zool., 19, 1895, p. 52; Jordan and Evermann, Bull. U. S. Nat. Mus., 

 47, pt. I, 1896, p. 698. 



Gambnsia jonesii Regan, Ann. IMag. Nat. Hist., (7) 19, 1907, p. 260; Biol. Centr. 

 Am., Pisces, 1907, p. 97, pi. 12, fig. 8. 



Pseudoxiphophorus jonesii Regan, Proc. Zool. Soc. London, 1913, p. 993. 



1 Miller, in recording specimens from Guatemala, gave the dorsal rays as 10 to 17, 

 but no one else has found fewer than 14 rays in the dorsal fin of any specimen of 

 this species found so far south. Perhaps Miller confused some other species with 

 the present one. 



