OCT., 1916. MAMMALS, COLLINS-DAY EXPEDITION OSGOOD. 209 



cave in front; the nasals end posteriorly in a point which greatly exceeds 

 the endings of the premaxillae. As compared with the skull of A. 

 cursor, that of A. dayi shows a slight resemblance in the development 

 of the parietal ridge, but the entire skull is so much deeper and heavier 

 that detailed comparison is unnecessary. 



Measurements. Average of ten adults: Total length 198 (186-214); 

 head and body 119 (110-134); tail 79 (75-84); hind foot 26 (25-27). 

 Skull of type: Greatest length 30.8; basilar length 24.8; zygomatic 

 breadth 15.6; interorbital constriction 5.6; median length of f rentals 

 10.5; interparietal 7.5x1.7; nasals 11.7x3.9; palatine foramina 7.4x2.8; 

 diastema 8; median length of zygomatic plate 3.3; upper toothrow 4.9. 



Remarks. Although having considerable color resemblance to 

 Akodon a. baliolus, this species differs from it so widely in cranial char- 

 acters that it is probable it has no close affinity and its nearest relatives 

 perhaps are to be sought among the species of eastern Brazil. The only 

 available species of this region which shows even slight similarity is 

 A. cursor, but this is smaller and paler and has a relatively low flattened 

 skull. 



A series of thirty-nine specimens of this new species was obtained 

 mostly about the half-dozen native huts forming the small village of 

 Todos Santos. All of them give evidence of having been very fat and 

 many have white hairs scattered through the pelage of the rump and 

 back, both features being possible indications that they were leading 

 slightly abnormal existences. Their presence in the village in large 

 numbers was doubtless due to the prevalence of heavy rains and floods 

 in the surrounding dense forest. 



Dasyprocta variegata subsp. VARIED AGOUTI. 



Two specimens, Porto Velho, Brazil. 



These are provisionally referred to this species of which no typical 

 examples are at hand. 



Proechimys brevicaudus securus Thomas. SPINY RAT. 



Six specimens (2 ad., 4 yg.), Todos Santos, Chapare' River. 



These are referred to this form largely on geographic grounds. So 

 far as can be determined from comparison with descriptions, they com- 

 bine the characters of P. securus and P. bolivianus, having the short 

 foot of the one and the long narrow skull of the other. Their resem- 

 blance to P. brevicaudus is striking not only in cranial characters but also 

 in external appearance, especially when the variability of brevicaudus, as 

 previously shown,* is considered. In one specimen there is consider- 



*See Field Mus. Nat. Hist., Zool. X, p. 168, 1914. 



