PROECHINOMYS. 385 
tebre at the posterior border of the pelvis. The fifth caudal is 
abnormal, the posterior half having apparently been lost by absorp- 
tion. This interesting fact was ascertained by Mr. F. M. Chapman,* 
who also states that on skinning specimens the tail easily broke 
away at the fifth caudal vertebre. So frequently does the loss of 
the tail occur, that in Trinidad the natives believe there are two 
species, those with tails, and the tailless. 
76. +Proechinomys. Spiny Rats. 
IL—; P=; oe = 90. 
Proechimys (sic) Allen, Bull. Am. Mus. Nat. Hist., 1899, p. 264. 
Type Echimys! trinitatis Allen & Chapman. 
Echimys (sic) Geoff. St. Hil., Ann. Scien. Nat., 2me Sér., x, 1838, 
Pp. 125. (mec G. Cuvier, 1809.) Jd. Mag. Zodl., 2me Sér., 
1840, p. 30. 
Nasals very long, rounded anteriorly, narrowing posteriorly, and 
longer than premaxille; orbital constriction slight, greatest width of 
skull at fronto-parietal suture; bulle large, converging to a point 
anteriorly; interpterygoid fossa broad, widest anteriorly; processes 
of the pterygoids long and broad, shaped somewhat like the head of 
a spear, pointed, the exterior half twisted outward and lying parallel 
with axis of skull; palate short, wide, posterior margin with V-shaped 
notch; incisive foramina broad, rather short; root of upper incisor 
curving backward to anterior base of zygoma; molar pattern rather 
simple, upper premolars with two external and two internal loops, 
the molars with two internal; lower molars with two external loops. 
Lower part of mandible broadly flattened and rounded outward, 
narrowing anteriorly to angle, which terminates in a short pointed 
process; condyle very broad, slightly rounded; coronoid process 
short, and pointed backward. 
KEY TO SPECIES AND SUBSPECIES. 
PAGE 
A. Hands and feet ashy brown.............. P. semispinosus 386 
Benes and feet dull whitish. .........2..0...). P. centralis 386 
C. Hands and feet brown. 
eDOCS, atk £tOUS 9. ul wt oe P.c. chiriquinus 387 
TOYS EC Vg oie 0 2) sa ne ee ee P.c. panamensis 387 
c. Above deep ferrugineous and brownish black...P. burrus 388 
* Bull. Amer. Mus. Nat. Hist., 1893, p. 226. 
Tf eytvoc, woo =Ecuinomys nec Echimys=PROECHINOMYS. 
