544 Mr. O. Thomas on new 
find in the upper jaw, behind the large canine-like J. 1, and in 
the lower jaw, behind the similarly constituted J. 2, a series 
of four teeth, which, especially in the upper jaw, are very 
similar to each other, as an adaptation to the conditions under 
which these two amphibious Insectivores obtain their food, 
and to the change in their diet. We are confronted with a 
degeneration, but in combination also with adaptation, whereby 
(especially in the case of Potamogale, which appears to be 
more exclusively piscivorous than Limnogale) an approxima- 
tion is furnished to the dentition of the Pinnipedia*. There 
is, however, this difference, that while in the case of the latter 
the entire dentition is now exclusively subservient to the 
functions of seizing and holding, in the Insectivores in 
question these are confined to the antemolars, since, as proved 
by the number and shape of their molars, they cannot, for the 
present at any rate, dispense with the mastecatory apparatus. 
LXVI.—Descriptions of new Bats and Rodents from America. 
By OLDFIELD THOMAS. 
Dasypterus ega xanthinus, subsp. n. 
Apparently similar in all essential characters to D. e. typicus, 
in spite of the wide difference in locality, but distinguished 
by the clearer yellow of the back, gradually brightening 
backwards until on the hairy part of the interfemoral the fur 
is quite fulvous. Under surface dull fulvous from chin to 
anus, the belly-hairs blackish basally, then lght fulvous 
gradually deepening to their tips. In the typical South- 
American forms the back is dirty whitish, with dark tips to 
the hairs, and there is little or no fulvous on the under surface. 
Dimensions of the type (male) :— 
Forearm 47 millim. 
Head and body ft 68 ; tail t 48; hind foot with claws f 10; 
ear T 16. 
Skull: greatest length 16°2, greatest breadth 11:4; breadth 
of rostrum at posterior edge of large premolar 7. 
Hlab. Sierra Laguna, Lower California. Six specimens 
examined. 
D. ega is not included at all in Mr. G. §. Miller’s admir- 
able monograph of the Vespertilionide found north of Panama, 
so that its occurrence in Lower California is a most remark- 
able and unexpected fact, considering the extent and com- 
pleteness of the collections he worked from. 
* As regards the Pinnipedia cf, W. Leche, ‘Zur Entwicklungs- 
geschichte des Zahnsy stems der Siugethiere, I.’ (Stuttgart, 1895), p. 66, 
+ Measured in flesh by collector. 
