16 ARKIV FÖR ZOOLOGI. BAND 14. N:0 4. 



M. affinis costaricensis appears, to judge as well from 

 the descriptions as from actual specimens from Costa Rica, 

 to be generally darker than the present specimens, and espe- 

 cially to have the blackish of the head extending much fur- 

 ther backwards. At the same time the white markings on 

 the head are said to be absent or reduced to mere traces 

 (J. A. Allén). If these characteristics are constant, the 

 present specimens cannot be referred to M. a. costaricensis. 



M. affinis affinis Gray is less dark than J/. a. costari- 

 censis and somewhat smaller. According to J. A. Allén the 

 condylobasal length of the skull of the former averages »about 

 7 mm shorter, and the zygomatic breadth about 2 mm less» 

 (1. c. p. 100). According to the tables of measurements com- 

 municated by the same author (1. c. pp. 109 & 110) the 

 average of 5 males of costaricensis is with regard to condylo- 

 basal length 49,6 mm and with regard to zygomatic breadth 28, 

 while the same average measurements for 6 males of affinis 

 are resp. 47,7 mm and 27,2 mm. This gives a difference in 

 condylobasal length of 1,9 and in zygomatic breadth of 0,8 

 mm. The first statement in the text is thus probably due 

 to a misprint. 



The average of the condylobasal length of 6 adult males 

 of the present collection is about 50,3 mm thus rather similar 

 to the same of M. a. costaricensis. There is consequently in 

 this respect nothing prohibiting an Identification with the 

 latter, but the true M. affinis affinis appears to be too 

 small to be considered. 



Taczanowski's description of M . macrura gives no infor- 

 mation about cranial dimensions, so that no comparison can 

 thus be made in this respect. His Communications about 

 the colour may be said to agree, at least with the darker 

 specimens of the present collection. The same is also the 

 case with the exteriör dimensions, except perhaps the size 

 of the hind foot, which appears to be rather larger in the 

 type of macrura. Until a satisfactory description with cra- 

 nial measurements of the true M. macrura Taczanowski is 

 obtained, it appears impossible to ascertain, whether the 

 Weasel of Ecuador is identical with that of Peru, or if it is 

 an intermediate link between the same and the one called 

 M. affinis costaricensis. It is, however, not specifically dif- 



