468 PROCEEiDINGS OF THE' NATLONiAL MUSEUM vol. loi 



the same in both, except for the above-mentioned reversal. Other 

 differentiating characters found in nigrum but not in rosaceimi are 

 ventral black bands, shorter hind leg (reaches elbow in rosaceimi), 

 and a different phalangeal formula (2-2-3-4-2 in rosaceum) on the 

 foot. The last may not be of taxonomic significance, as variants in 

 phalangeal formulae do occur occasionally. 



AMBYSTOMA ROSACEUM SONORAENSIS, new subspecies 



Types.— Roloty^Q : U.S.N.M. No. 17253, larva ; P. L. Jouy collector. 



Paratypes : U.S.N.M. Nos. 17254-17256, topotypic larvae. 



Type locality. — Sonora, 32 miles south of the Arizona border. 



Diagnosis. — Maximum known total length 102 mm. (larva) ; color 

 chocolate-brown (in alcohol) with irregularly shaped small yellowish 

 blotches, which tend to form longitudinal bands ; belly uniformly pale ; 

 toes failing to reach elbow by 6 mm. when limbs are adpressed ; web 

 involving only metacarpals and metatarsals. 



Description. — Head width (12 mm.) contained in body length 

 about 4.5 times ; diameter of eye 2.5 mm. ; gill rakers 20 on middle arch ; 

 gills partially absorbed; tail fin (largely absorbed) originating well 

 posterior to insertion of hind legs; 10 and possibly 11 moderately 

 developed costal folds. Maxillary-premaxillary teeth about 33 on a 

 side ; pterygoid teeth about 10-10 ; vomerine teeth about 30-30 ( ? ) ; 

 splenial teeth in more than one row and about 50-50 in number. 



Limbs well developed ; metacarpals and metatarsals not quite fully 

 webbed; phalangeal formula of hand, 2-2-3-2, of foot, 2-2-3-4r-2. 



Color. — Dark brown "ground color" extends to edge of, but not or 

 barely onto, venter ; tail fin remnant colored same as body. Otherwise 

 pattern similar to that of A. r. nigrum (fig. 91) . 



Measurements of holotype in millimeters. — Total length 102 ; body 

 length 55 ; tail length 47 ; length of snout 4.5 ; interorbital 5 ; internasal 

 5; diameter of eye 2.5; distance between choanae 5; snout to arm 

 insertion 19.0. 



Remarks. — Paratype U.S.N.M. No. 17254 is similarly colored except 

 that the light lateral band is more distinct, being continuous for the 

 length of the body. The other two paratypes are too small (40 mm.) 

 and too poorly preserved to be of much diagnostic use. It is apparent, 

 however, that they are not so heavily pigmented as the holotype, the 

 dark and light colors occupying equally extensive areas. The larger 

 paratype is about equal in total length to the types of Taylor's (1941) 

 rosaceum (87 and 85 mm.) but is almost as heavily pigmented as the 

 holotype of sonoraensis. Thus it is apparent that the diagnostic differ- 

 ences in coloration between r. rosaceum and r. sonoraensis are not age 

 differences. A. r. sonoraensis is easily differentiated from nigrum by 

 occurrence in the latter of ventral black bands. The lesser phalangeal 



