MEXICAN AMPHIBIANS—TAYLOR AND SMITH 525 
Order CAUDATA Oppel, 1811 
Family AMBYSTOMIDAE Hallowell, 1858 
Genus SIREDON Wagler, 1830 
SIREDON MEXICANUS (Shaw) 
Gyrinus meaicanus SHAW, Naturalist’s Miscellany, vol. 9, 1798, pls. 343, 344 
(México, restricted to Lake Xochimilco). 
Siredon mexicanum Bairp, Journ. Acad. Nat. Sci. Philadelphia, ser. 2, vol. 1, 
1849, p. 292. | 
A series of 47 specimens was obtained. Cataloged are U.S.N.M. 
Nos. 116585-116594 from Lake Xochimilco, D. F., January 25 and 
September 7, 1939. Another specimen (H.M.S. No. 11336) was 
purchased September 29,1939, from a resident of San Andrés Mixcoac, 
México (near Chalco), in the vicinity of which the specimen was said 
to have been collected, in a small lake. 
A specimen of Rhyacosiredon altamiranit was given to one of us 
(Smith) by Dr. Manuel Maldonado K. It purports to have been 
taken at Lake Xochimileco. If this species occurs there, it may form 
the basis of oral reports that Siredon mexicanus occasionally transforms 
in nature. 
SIREDON LERMAENSIS Taylor 
Siredon lermaensis Taytor, Univ. Kansas Sci. Bull., vol. 26, No. 12, 1939 (Nov. 
27, 1940f), pp. 427-430, pl. 48 (Lake Lerma, east of Toluca, México). 
A series of 107 specimens was acquired at the village of Lerma on 
the edge of Lake Lerma, March 4 and September 30, 1939. These 
consist of young, neotenic larvae and transformed adults. The 
adults are present only in the March series. Fifteen specimens 
(U.S.N.M. Nos. 116570-116584, all topotypes) are cataloged. 
The two youngest larvae examined measure 51 mm. from snout to 
vent; the tail of one measures 41 mm., while that of the other is 
partly missing. At this age the maxillary-premaxillary teeth are 
35-35, well developed, and very unequal in size. The pterygoid 
teeth, somewhat separated from the vomerine series, reach to the 
posterior level of the choanae and consist of four short diagonal rows 
of four teeth, each with one or two rows of two (or one) teeth. The 
vomerine groups are widened, and each consists of 11 rows of three to 
six teeth (or if counted in another direction six rows of a varying 
length with 3 to 11 teeth). The groups are separated by a diastema, 
medially. The splenial series have about 40 teeth, arranged in 
short transverse rows of two or three teeth each. The mandibular 
teeth are similar to the maxillary-premaxillary series in number. 
They are arranged rather irregularly in the jaw. 
In color these young are brownish gray (under the lens the pig- 
ment shows as a reticulation, with circular skin glands evident as 
