n8 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. V. 



two small ones under the belly, a single one behind the anus, which 

 lies between the fin and the single one; the tail is not forked; lastly, 

 this fish has a long fin on the back, a little above the fin which is 

 under the belly. 



" 'We know of some viviparous fishes in our seas, such as loach, 

 etc. ; most of these have a smooth skin without any scales. The 

 needle of Aristotle is viviparous, and yet covered with broad and hard 

 scales. I have caught some that had young ones still in their womb. 

 As to these viviparous fishes, it is a particular and new sort, and we 

 are obliged to Don Alzate for making us acquainted with it. It breeds 

 in a lake of fresh water near the City of Mexico.' 



"This is, so far as known, the earliest notice of the viviparity of 

 Cyprinodontids. The mode of consorting together (exaggerated in 

 the account) is common to a number of representatives, of the family, 

 and is alluded to by Prof. Agassiz in a name (Zygc^iectes , i. e., swim- 

 ming in pairs) conferred on one of the genera of the family." 



Subfamily Orestiinse. 

 48. Characodoii Giinther. 



Characodon Gunther, Cat., vi, 308, 1866. (Type, Characodon 

 lateralis Gunther.) 



Body rather deep, compressed; mouth small; teeth small, fixed, 

 the outer series bicuspid, with a villiform band behind them; origin 

 of dorsal fin nearly opposite that of the anal ; anal fin with its first 5 or 

 6 rays short and stiff and separated from the rest by a shallow notch ; 

 alimentary canal short, i to 1% times the total length of the fish; 

 species viviparous. 



KEY TO THE SPECIES OF CHARACODON. 

 a. Dorsal and anal fins very long, each of more PAGE 



than 20 rays multiradiatus 119 



aa. Dorsal and anal rays shorter, each of less than 



20 rays. 



b. Scales large, 30 to 35 in the lateral series, 

 c. Dorsal fin slightly in advance of origin of 

 anal, its origin about midway between tip of 

 caudal and tip v of snout, 

 d. Anal rays 13 ; scales 30 to 32 ; about 9 teeth 



in the upper jaw and about 14 in the lower ei^eni 119 



dd. Anal rays 15 or 16; scales 35; about 14 

 teeth in the upper jaw and about 16 to 18 

 in the lower . . .variatus 120 



