Vol. XXV, pp. 9-10 January 23, 1912 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



A NEW WEASEL FROM COSTA RICA. 



BY E. A. GOLDMAN 



The weasel of Costa Rica has been commonly referred by 

 authors to Mustela affinis Gray, of Colombia, but in making 

 general comparisons in connection with the identification of 

 specimens from Panama I find that Costa Rican examples rep- 

 resent a new form which is described below. 



Mustela costaricensis sp. nov. 

 COSTA RICAN WEASEL. 



Type from San Juse, Costa Rica. No. IHKo J'" 1111 ^ adult, U. S. Na- 

 tional Museum, collected by Dr. C. H. Van Patten. 



General characters. — Closely allied to affinis, but somewhat larger; color 

 about the same; audita! bullae relatively larger, less flattened. Similar 

 to tropirnlis and perdus, but white facial markings reduced to narrow 

 streaks, or absent ( broad and conspicuous in tropicalis and perdus). 



Color. — Upper parts, including outer sides of legs and feet, blackish 

 brown or chestnut, passing gradually into nearly pure black on neck and 

 head; under parts from median line of belly to upper part of thighs and 

 arms varying from huffy yellow to orange buff, paling on throat and chin 

 to pure white; white facial markings absent in type, but present in some 

 specimens, varying from a few isolated hairs to very narrow white streaks 

 across forehead and cheeks; tail like hack, except tip, which is black all 

 round. 



Skull. — Similar to that of affinis, hut larger ; hraincase more elongated; 

 audita] bullae relatively larger, less flattened, the anterior borders pro- 

 jecting more prominently from cranium. General form much as in trop- 

 iralix and perdus, but audital bulla? flatter. 



Measurements. — Skull of type (skin measurements not available) : Con- 

 dylobasal length, ">:'>. 7; zygomatic breadth, 29; interorbital breadth, 

 11.7; audital bulla?, 14.5 x 8; alveolar length of upper molariform tooth- 

 row, 12.7. 



Rirnarks. — The Costa Rican weasel is somewhat intermediate in char- 



1— Proc. Biol. Soc. Wash.. Vol. XXV, 1912. 



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