Family I. SIRENID.E. 



Body elongated, eel-like. Posterior limbs wanting ; the anterior mod- 

 erately developed, with three or four fingers. External gills present 

 during whole of life. One to three branchial slits on each side of the 

 neck. Premaxillaries and dentaries without teeth, and covered with a 

 horny sheath. Teeth on the splenials. Vomers provided v/ith teeth, 

 which form two converging patches on the roof of the mouth. No maxil- 

 laries present. Contains two genera, each embracing a single species, 

 both confined to North America. 



Key to the Genera of Sirenidce. 



A. Fingers four ; branchial slits usually three. Siren, p. 8. 



AA. Fingers three ; branchial slit one. Pseudobranchus. 



Pseudobranchus has not been found north of Georgia and Florida. 



Genus SIRE5T, Linnwus. 



Siren, Linureus, 1765, 95; i, 311; Boulenger, 1882, 28, 86; Cope, 

 1889, 51, 225. 



Hand with four fingers. Jaws with horny sheath. Vomerine patches 

 of teeth broad. Tongue broad, free in front. External gills and branchial 

 slits, three. Eyes distinct, but without lids. 



Siren lacertina, Linn. 



Mud-eel. Siren. 



Siren lacertina, Linnreus, 1765, 95, i, 311; Holbrook, 1842, 5i, v. 101, 

 pi. 34; Boulenger, G. A., 1882, 28, 87; Cope, E. D., 1889, 51, 226; 

 Barton, B. S., 1821, ^0. 



Body long, slender, nearly cylindrical ; about twelve times as long as 

 the head is broad. Head flat above, sides tapering to the blunt snout, 

 which overhangs the mouth. Gill slits three. External gills three 

 pairs ; but these appear to be abortive in the young up to six inches in 

 length. Eyes small, without eyelids. Premaxillaries distinct, toothless, 

 covered with a black horny sheath. Vomers and palatines distinct, each 

 with several rows of small teeth. Dentaries also toothless, and covered 

 with a black horny sharp-edged sheath. Teeth on splenials (just below 

 hinder ends of dentary sheath). Tongue free on sides and in froat. 



Anterior limbs well developed, short, furnished with four digits each. 

 No trace of hinder liml5s. Body and tail crossed by numerous furrows ; 

 about thirty of these from fore legs to vent. Tail compressed, with a fin 

 above and below ; its length somewhat more than one-third the total 

 length, terminating in a sharp point. 



