200 ON THE DIFFERENT SPECIES OF OTTER. [Apr. 2, 



that one of the hest and most convenient methods of preserving 

 Otters for scientific purposes is simply by cutting off their heads 

 and putting these into spirit. By this means the characters of the 

 nose-pad are preserved, the skull is available for examination if 

 necessary, and tlie collector is saved the trouble and expense inci- 

 dental to skinning or sending home the whole animal. Where this is 

 done, however, the sex of each individual should be carefully noted, 

 and marked on a label attached to the head. 



Finally it may be of use to give a few of the more diagnostic 

 cranial measurements of the Otters above recognized, since a com- 

 parison of the basal length, interorbital breadth, and "lobe-measure- 

 ment" will enable students in most cases to recognize the species 

 from these few dimensions only. The species are here arranged in 

 order of size, based upon the basal length. 



The " lobe-measurement " of p^* is the distance in a straight antero- 

 posterior line from the most anterior |)oint of the tooth to the most 

 posterior point of the hinder convex edge of its inner lobe. This 

 measurement includes, it is true, a part of the tooth not belonging 

 to the inner lobe, but there appears to be no other way of satisfac- 

 torily estimating the size of the lobe. The " basal length " is of 

 course from the basion (back of the basioccipital in the median 

 line) to the gnathion (most anterior point of the preinaxillse). The 

 fairly constant "interorbital" must not be confused with the varying 

 and changeable " intertemporal " breadth. 



Basnl 

 length. 



Lutra brasiliensis, 2 141 '5 



,, capensis {6) 1 29 



„ (2) 118 



,, barany, S 118 



» (?) 108-5 



„ vulgaris, S 1 14 



„ (?) 104-8 



,, sumatrana ( cJ ) (c.) 112 



., . ? (c.) 98 



„ canadensis, ^ 10 To 



„ paranensis '■ 97 



,, maculicollis, S 9G-2 



„ feliua, S 80-3 



» „ ? 84-2 



,, cinerea, d" 82*2 



» ? (c.) 820 



^ Tho sex-raark is here, as elsewhere, placed witbin brackets where the sex 

 is only presumed from the form or relative size of the skiJl, and is not known 

 from external or historical evidence. 



^ From the type specimen of L. plaicnsis, Waterh. 



