544 Mr. 0. Thomas on yiew 



find in the upper jaw, behind the large canine-like /. 1, and in 

 the lower jaw, behind the similarly constituted I. 2, a series 

 of four teeth, which, especially in the upper jaw, are very 

 similar to each other, as an adaptation to the conditions uuder 

 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 Fokimo/jale, 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 masticatory apparatus. 



LXVI. — Descriptions of new Bats and Rodents from America. 



By Oldfield Thomas. 



Dasypterus ega xanthinus, subsp. n. 



Apparently similar in all essential cliaracters 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 light 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 f 68 ; tail t 48 j hind foot with claws f 10 ; 

 earf 16. 



Skull : greatest length 16'2, greatest breadth 11*4 ; breadth 

 of rostrum at posterior edge of large premolar 7. 



IJab. Sierra Laguua, Lower California. Six specimens 

 examined. 



D. ega is not included at all in Mr. G. S. Miller's admir- 

 able monograph of the Vespertilionidse 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 Zahnsystems der Saugetbiere, I.' (Stuttgart, 1695 j, p. bO. 

 t Measured in tiesh by collector. 



