136 Mammalia of Southern Brazil. 
30. MUS ALEXANDRINUS Gcoffr. 
Chapada. With a litt^ of young. 
31. MuS DECUMANUS L. 
Sao Joao. 
ECHINOMYIDyE. 
32. Dactylomys amblyonyx Wagner. 
Three skins with skeletons, from Sao Joao. 
These specimens agree with the descriptions given by Hensel 
and Burmeister. The dentition differs from that of the D. typus 
Geoff, as figured by Geoffrey ^ and F. Cuvier,f in having the two 
component V-shaped columns in both jaws united by a narrow 
isthmus, as is the case in the columns in Echinomys. This fusion is 
probably due to the age of the specimen, as it takes place on wear- 
ing in the genus Echinomys. Another character is the transverse 
lamina-like anterior plate of the first inferior molar (premolar), 
which is represented by a cylindric column in the D. typus, accord- 
ing to the authors cited. The superior molars are not nearly so close 
together anteriorly as is represented by St. Hilaire to be the case in 
the D. typus, and they diverge a little posteriorly. 
33. Sphingurus prehensilis Linn. 
Three skins with skeletons, and one skull, from Chapada. 
34. Sphingurus sericeus sp. nov. 
All the inferior surfaces with the forearm and lower leg destitute 
of spines, but clothed with a silky.hair of which the basal half is black 
and the terminal half silvery white. Superior surfaces to the middle 
of the length of the tail, spinous ; the spines concealed by long silky 
hair except on the head, nape, and proximal half of the tail. This 
hair is much longer than that on the inferior surfaces, and is simil- 
arly colored, i. e., with the basal half black, and the terminal half 
silvery, but more inclining to gray than on the inferior surfaces. 
The spines are an inch and a half long, becoming shorter on the tail, 
the front, and the upper lip, and are rather slender, and on the nape 
are decurved. Those on the interorbital and suborbital regions are 
still more slender. The nasal, preorbital, and subcaudal regions are 
