PROECHINOMYS. 3H5 



tebrae 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 vertebras. 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. fProeehinomyg* Spiny Hats. 



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 Se"r., x, 1838, 

 p. 125. (nee G. Cuvier, 1809.) Id. Mag. Zool., 2me Se"r., 

 1840, p. 30. 



Nasals very long, rounded anteriorly, narrowing posteriorly, and 

 longer than premaxillae; orbital constriction slight, greatest width of 

 skull at fronto-parietal suture; bullae 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 



B. Hands and feet dull whitish ....... ........... P. centralis 386 



C. Hands and feet brown. 



a. Above dark rufous .................... P. c. chiriquinus 387 



b. Above paler .......................... P. c. panamensis 387 



c. Above deep ferrugineous and brownish black. . .P. burrus 388 



*Bull. Amer. Mus. Nat. Hist., 1893, p. 226. 



^eXtvoff, /zu(T=EcHiNOMYs nee Echimys= PROECHINOMYS. 



