526 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 95 
cream spots). The chin and venter are much lighter, but some pig- 
mentation is evident under a lens. 
A specimen of 62 mm. is dark grayish black above, the belly and 
limbs a little lighter, but in turn much darker than the chin. The 
teeth are much the same as in the preceding larva, except that there 
are more rows of splenial teeth and each of these may have four or 
five teeth. The palatal pit, indicated in the youngest as a deep, 
very narrow pit, is larger, but still deep and slitlike. The fold at 
the corner of the mouth is more ample. 
In the largest larvae, 118-125 mm. from snout to vent, the vomerine 
and pterygoid (palatine) series are arranged in a single more or less 
continuous row on each side, tending to form a curved arch, broken 
medially. The splenial series, now with 40 to 45 teeth, are in a 
single somewhat irregular row. 
The smallest transformed specimen measures 78 mm. from snout . 
to vent; the tail, 68 mm. The splenial teeth have disappeared; the 
vomeropalatine series form an angular arch; however, the two series 
are narrowly separated medially. The palatal pit is circular, deep, 
and much larger than the choanae. The tongue has developed. 
Another specimen, transforming but with a trace of the gills, meas- 
ures 108 mm. from snout to vent; tail, 76 mm. It is possible that 
the last mentioned transformed from a neotenic female, while the first 
mentioned adult transformed from an immature larva. 
Genus RHYACOSIREDON Dunn, 1928 
RHYACOSIREDON ALTAMIRANI (Dugés) 
Amblystoma aliamirani Ducks, Description d’un axolotl des montagnes de Las 
Cruces (Amblystoma aliamirani A. Dugés), Imprimerie du Ministére de ‘‘Fo- 
mento,” 1895, pp. 1-6, 1 pl. (““Manantial de los Axolotes en la Serrania de las 
Cruces perteneciente al Valle de México’’). 
Rhyacosiredon altamirani Dunn, Proc. New England Zool. Club, vol. 10, 1928, 
pp. 85-86. 
A series of 17 specimens comes from the Ajusco range southwest 
of México (City), chiefly in the vicinity of the Lakes of Zempoala 
(Cempoala) in Morelos and México. The following are cataloged: 
Zempoala Lakes, July 25, 1939, and August 28, 1940 (U.S.N.M. 
Nos. 116599-116612); Desierto de los Leones, D. F., June 9, 
1940 (U.S.N.M. Nos. 116597-116598); and Cafiada de Contreras, 
D. F., January 16,1938 (U.S.N.M. No. 116613). Those from the 
last two localities were presented to Smith by Dr. Rafael Martin 
del Campo, of the Instituto de Biologia in México (City). One other 
specimen (H.M.S. No. 12836) is labeled Lake Xochimilco, D. F., 1939 
(see discussion of Siredon mexicanus). 
