Oct., 1916. Mammats, Cottins-Day ExpEepiTion—Oscoop. 209 
cave in front; the nasals end posteriorly in a point which greatly exceeds 
the endings of the premaxille. 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. frontals 
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 Rar. 
Six specimens (2 ad., 4 yg.), Todos Santos, Chaparé 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. 
