Mr. O. Thomas on the Echimyine. 299 
On the other hand, D. perwanus has a very hairy tail, which 
is really quite bushy for the basal half, and well clothed to 
the more or less tufted end, the scales being only just percep- 
tible between the hairs on the subterminal fifth. ‘This diffe- 
rence gives the animals quite a different appearance, and no 
doubt indicates a difference in habits. 
In the teeth, while the outer re-entrant angles in the upper 
molars of D. dactylinus are of equal extension throughout, 
running from one-half to three-fifths across each tooth, in 
D. peruanus their angles, similar to those of dactylinus in 
the premolar and m*, are in m? and m? of unequal extension, 
the posterior running across nearly to the inner edge of the 
tooth, while the anterior is as in the other teeth. 
Under these circumstances I would suggest that D. peru- 
anus should form the type of a new SE OBSLOS, which might 
be called Lachnomys. 
The claws of Lachnomys, both before and behind, are 
absolutely as in true Dactylomys. 
'THRINACODUS. 
This genus is very nearly allied to Dactylomys, but differs 
in the character of its claws, which are normal throughout, 
except that the second hind pair is modified into an oblique 
asymmetrical nail, as in many other members of the family. 
Its tail is intermediate in hairiness between that of true 
Dactylomys and of Lachnomys. ‘The angles of its molars 
approach those of the latter form. 
The specimens available come from three different regions 
—Merida, Bogota, and Antioquia, the last being the type- 
locality. 
Those from Merida have distinctly larger skull and larger 
teeth, and might be distinguished specitically. 
Thrinacodus edax, sp. n 
Colour and other external characters as in 7. albicauda, 
but the tail completely white along the under surface, the 
terminal half above also white ; line of demarcation tairly 
abrupt. 
Skull larger than in 7’ albicauda. Molars broader and 
heavier. In an adult topotype of albscauda the breadth 
across the most distant points of the two premolars is 8°5 mm., 
and the breadth of each tooth, measured diagonally from the 
front of the two inner points to the second of the outer points, 
is 4°0 mm., while in edax these measurements are respec- 
tively 9°2 and 4:6 mm.; and the other teeth are all in 
proportion. 
