O34 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 95 
Vomerine and palatine series of teeth nearly continuous except for 
a median diastema; choanae elongate longitudinally; about 20-22 
palatine teeth; about 43-43 vomerine teeth, both series irregular; 
maxillary-premaxillary teeth about 70-70; mandibular series about 
same, but many teeth hidden by gums; no tongue. 
The specimen is a female with nearly mature ovarian eggs; the 
cloacal region is folded, with some papillae or papillate folds. U.S. 
N. M. No. 116755 has numerous black ocelli on head and back and on 
dorsal fin. A few other adult larval specimens show the same ocelli; 
some of the younger specimens show traces of the upper dorsal series 
of neuromast organs. 
In a young specimen the vomerine series are widened, the teeth tend- 
ing to form six or seven diagonal series; the pterygopalatine teeth are 
likewise arranged in several irregular series; length 85 mm. snout 
to vent. 
Remarks.—sThe neotenic and other larvae occurring in Zumpango 
are referred to this form although there is no absolute proof of con- 
specificity. All the larvae, despite certain apparent differences, 
seem to belong to a single species. The species must be regarded as 
one apart from Ambystoma velasci. The coloration and markings of 
both young and adult are different; the shape of the body and head, 
the longer, slenderer tail, and the very different character of the trans- 
formed adults confirm the fact that two different animals are involved. 
Differences between this species and A. ordinaria and A. amblycephala 
are such that there is no opportunity for confusing them. There 
may be a relationship with A. bombypella, but differences in color 
markings and the character of skin and tail amply distinguish them. 
Family PLETHODONTIDAE Gray, 1850 
Genus THORIUS Cope, 1869 
THORIUS PENNATULUS Cope 
Thorius pennatulus Corr, Proc. Acad. Nat. Sci. Philadelphia, vol. 21, 1869a, 
pp. 111-112 (Orizaba, probably near the city). 
An extraordinary series of 723 specimens was collected on the 
side of a peak in the valley near Cuautlapan, Veracruz, in January, 
February, July, and August 1940. These specimens were found un- 
der débris of various types, and very frequently around the edges of 
boulders under living plants, which often formed a thick mat about 
the boulders. 
Cataloged in the collection are U.S.N.M. Nos. 111012-111037, 
111039-111067. U.S.N.M. No. 111017 is designated a neotype, 
since no authentic types are known to exist. 
This is the most diminutive salamander yet discovered in México. 
There are 13 well-defined costal grooves, strongly pendant swellings on 
