152 Mr. O. Thomas on new small 



the two species only & armata was represented in our 

 collection, but judged it prudent to appeal for assistance to 

 the great experience of Dr. Norman, who requests us to state 

 that his Plymouth specimen, which by some unaccountable 

 error was recorded as S. frontalis, proves on re-examination 

 to be a female of S. armata. We have examined Mr. Gar- 

 stang's specimen : it is a female of S. armata, showing 

 characters which are fully covered by the range of variation 

 in the examples of this species in our own collection. We 

 further learn from Dr. Norman that a tube of Siriella received 

 by him from this Laboratory as 8. frontalis contains only 

 S. armata. S. frontalis must therefore be erased for the 

 present from the British list, since Dr. Norman now thinks 

 that Gosse's Mysis producta is in all probability 8. armata. 



We are requested by Dr. Norman to state that his descrip- 

 tion of S. frontalis was drawn up from that of Sars compared 

 with Adriatic specimens received from Dr. Claus. Its 

 validity is therefore in no way impaired by the accidental 

 insertion of an erroneous record of locality. 



Laboratory of the 



Marine Biological Association, 



Plymouth. 



XXT. — On new small Mammals from South America. 

 By Oldfield Thomas. 



Oryzomys bceops, sp. n. 



Very similar externally to 0. laniger and 0. niveipes, but 

 really allied only to the latter. Fur long, soft and woolly. 

 General colour dull greyish brown, darker along the middle 

 line of the back. Under surface silvery greyish, the hairs 

 dull slate for their basal two thirds ; no trace of the buffy or 

 fulvous tone found in the other two species. Back of ears 

 scarcely darker than general colour. Hands whitish above ; 

 feet pale brown. Tail rather longer than head and body, 

 closely scaly, nearly naked, greyish brown, rather paler 

 below. 



Skull of the general type of that of 0. niveipes, but with 

 its anterior portion, from the front of the brain-case forwards, 

 markedly shortened and more delicate; fronto-nasal profile 

 quite flat, not convex ; nasals short and narrow ; interorbital 

 region narrow, concave mesially, its edges faintly marked, 

 neither rounded nor beaded ; anterior zygoma-root narrow, 



