ISO Mr. 0. Thomas on 



It was first obtained by tbe Autavotio Expedition of 

 ] 84 1-2 under Sir James Ross, and, later on, by tbe French 

 (^ape Horn Mission, iu wbose Zoolou:y (AFuridae written by 

 nivself) it is referred to as " Reithrudon c /i inch i I /aides." 1 

 owe to the kindness of Prof. Trouessart tbe h)an again of tbe 

 adult specimen 1 determined in 1890, and the transference 

 by exchange of an immature example from tbe same 

 locality. 



The original specimen was, imfortunately, ])ut in some 

 ])eeuliar preserving fluid, whicli has caused the skull, after 

 extraction, to shrink in drying. Its size, however, before 

 drying was quite tbe same as iu the French specimen, and its 

 teeth are still unaflcctcd. 



The Obtzomts of the Extreme South of South America. 



When in 1881 I described '■'■ Hesperumys {Calomys) 

 ro/jpiiigeri" no assertion as to the position of the type- 

 localilies Cockle Cove and Tom Bay was made, but the 

 stattnient on the labels that these places were in the Straits 

 of Magellan was generally accepted, and influenced later 

 determinations. Now, however, on finding that all other 

 Oryzomys from the Straits region are referable to O. magel- 

 hmicus, Benn,, including those from Orange Bay, Cape Horn, 

 1 have thought it })robable that some mistake has been made. 

 On examining Dr. II. W. Coppiuger's book, the "Cruise of 

 the 'Alert/" 1883, it at once appears that Cockle Cove and 

 Tom Bay arc not in Mhat is commonly called the Straits of 

 ^Magellan at all, but are in Trinidad Channel, at the north 

 end of Madre de Dios Island, West Patagonia, in 50° S. lat. 



Since O. coppinyeri is so closely allied to O. vwyellanicus 

 as practically to difl'er from it in nothing but its greater size, 

 this location is far more natural than in the Straits, near the 

 centre of the range of 0. mnyellanicus. 



The specimens obtained by tbe P'rench Transit of Venus 

 Expedition of 1882—3, named bv me Hesperomys coppinycri, 

 ])r(;ve on re-examiiiation to be typical 0. mayetlanicus^ 

 which is evidently common throughout this region. 



But a series from further north, in middle Patagonia, 

 equally referable specifically to O. magellanicus, prove to have 

 such uniformly longer tails as to deserve subspecific distinc- 

 tion, as follows : — 



Oryzomys mayellunicus miztirus, subsp. n. 



Size and other characters quite as in true magellanicus^ 

 bnt tbe tail averaging abfnit 130 mm. in length, in adults, as 

 compared with about 110-115 in the more soutberii form. 



