228 BULLETIN 31, UNITED STATES NATIONAL MUSEUM. . 



punctatus aud larvcie of Ambly stoma. lu Proteus the secoudary 

 branches are also present. The fibrillse in Siren present different con- 

 ditions, perhaps dependent ou the character of their environment as to 

 the abundance of water, etc., and indicating different degrees of fnuc- 

 tional efficiency. I have discussed this question under the head of the 

 family Sirenidoe. 



The body is rounded, subquadrate iu section, and displays an indis- 

 tinct median dorsal groove. The transverse grooves are distinct on the 

 sides and nearly meet on the belly, but are not distinct on the back. 

 They vary from thirty-one to thirty-seven in number. The larger speci- 

 mens generally have thirty-six and thirty-seven grooves, while smaller 

 ones frequently have only thirty-one and thirty-two. The specimens 

 with thirty-three, thirty-four, and thirty-five are of medium size ; but a 

 full- sized one from Georgia (I?5"o. 4535) has thirty-two, and a small one from 

 South Carolina (No. 10514) has thirty-four. It was on specimens present- 

 ing the characters of the smaller individuals above mentioned that the S. 

 intermedia of Lecoute was proposed. I can not distinguish it from the 

 ordinary form. The sldn is everywhere perfectly smooth. The tail is 

 compressed from the base to the extremity, and for its distal half is 

 quite thin. It has a strong dermal fin above and below. It commences 

 above opposite to the anterior extremity of the vent, and below about 

 one-fourth the length of the tail posterior to the vent. 



The branchial fissures, as remarked in the discussion of the supposed 

 retrograde metamorphosis of Siren, may be one, two, or three, on one or 

 both sides. In a series of small specimens from South Carolina (Xo. 

 14111) the fissures are as follows: 2-1, 3-2, 2-2, 2-2. In a similar 

 series from Georgia (No. 4535) they are 2-2, 3-3, 2-2 larger than last; 

 2-3 same size as last, and 3-3 fully grown. 



Measurements of No. 8349. 



M. 



Total length 714 



LengLli of head aod body 470 



Length to axilla - 082 



Length to first hrauchia 055 



Length to line of canthns of mouth 019 



Length to line of eye 014 



Length of fore-leg from axilla 0385 



Length of humerus from axilla 019 



Length of cubitus OIG 



Widtli between nostrils 0165 



Width between eyes 023 



Width of head 045 



Expanse of fore limbs extended '- 114 



Depth of tail at middle 065 



The general color is a dark lead-color, usually darker above than be- 

 low. There is in some specimens a yellow band, with irregular or badly 

 defined outline, extending around the muzzle and upper lip to the base 

 of the anterior branchia. In some specimens this band includes the chin ; 



