Sjrin^ Mats from South-eastern Brazil. 141 



b. Brain-case little ridged, andwitliout 



strong postorbiial angles. Palatal 



notch to middle of /»'-. 



«^. Larger; skull about 54 mm. 



Supraorbital edges scarcely 



beaded. Pterygoids spatulate. 



(Sao Sebastian Island, Sao Paulo.) 2. iheringi, Tbos. 



b^. Smaller ; skull about 51 mm. 



Supraorbital edges beaded. 



Pterygoids linear, (S.W. Rio 



Janeiro.) 3. dimidiatus, Giintli. 



B. With 3 lamiuse to cheek-teeth. — 

 Subgenus Trino^nys. 



c. Palatal notch to middle of m^. 



Tail with white terminal pencil. 



(Baliia and Minas Geraes.) 4. setosus, Desm. 



d. Palatal notch to front of wr. Tail 



dark above to end. (Bahia Pro- 

 vince.) 6. albispinus, I. Geoff. 



c'^. Sidesreddish. Skull more slender. 

 Incisors orthodont, 86°. (Madre 



de Dios Island, Bahia Bay.) . . 5 a. alhispinus albispinus. 

 (P. Sides brown. Skull broader and 

 shorter. Incisors more proodont 

 93 96°. (Lamarao, Bahia.) . . 5 b, a. sertonius, subsp. n. 



Details about P. roherti and iheringi will be found in the 

 orio;inal descriptions of those species. 



P.dimidialus was described by Giinther'^ as an immature 

 specimen without locality, presented by Lord Derby (B.M. 

 no. 51. 7. 21. 24). We know that its donor did obtain a 

 number of specimens from Rio Janeiro, and the skull agrees 

 so closely with those of two examples from Itatiaya, near to, 

 the Rio-Minas frontier, collected and presented by Prof. J. P. 

 Hill, that I have no hesitation in referring the latter to 

 Giinther's species. 



" Echimys setosus, Desm.," was the first described of the 

 group^ but was ignored by the other early writers, who con- 

 tributed synonyms to it as follows: — myosuros, Licht., 1820; 

 leptosoma, Bts., 1827 ; cinnamomeus, Licht., 1830 ; elegans,, 

 Lund, 1841 ; and fuliginosus, Wagn., 1842. The charac- 

 teristic white end to the tail is mentioned in connection with 

 most of these, and there does not seem to be any doubt as to 

 llieir reference. The typical skull, now in the Paris Museum 

 (No. A. 7787), though very imperfect, shows clearly the tri- 

 laminate teeth characteristic of Trinomys, and has its palatal 

 notch only penetrating to the middle of m^. Specimens 

 corresponding to this animal have been obtained at Lagoa 

 kSanta, Minas, by Lund and others, and at " Bahia,^' whence 



* P. Z. S. 1876, p. 747. 



