642 THE AMERICAN NATURALIST. (Vor. XXXV, 
7.6; length of palate to palatal notch, 21; to end of ptery- 
goid, 34; length of palatal foramina, 5.2; width of palatal 
foramina, 3; upper tooth row, 9.8; length of single half of 
mandible, 33.8; lower tooth row, 10.2. 
~ Remarks.— The San Miguel spiny rat is a slightly differ- 
entiated island form of the centralis series. It was very 
common in the island, and Mr. Brown easily took as many 
specimens as he wanted. It is known to the islanders as 
* Raton mockungay." They, however, believe the tailless 
individuals are a different animal. About one-third of the 
specimens taken were tailless. The animal was generally 
distributed throughout the island, and was often found living 
in the huts and sheds of the negroes, like the common rat. 
Mr. Brown took P. panamensis at Loma del Leon, Panama, 
and P. chiriqguinus at Divala, Chiriqui. 
Zygodontomys seorsus! sp. nov. 
Sixty-eight specimens, April and May. 
Type: No. 8490, old adult 4, Bangs Collection, Museum 
of Comparative Zoólogy. Collected May 5, 1900. 
Characters: Similar in color and general appearance to 
Z. brevicauda (Allen and Chapman) of Trinidad, but much 
larger, hind foot much bigger, tail less distinctly bicolored 
and more coarsely scaly. Skull larger, rougher, supraorbital 
heading heavier, transverse ridge where squamosal and supra- 
occipital meet more pronounced, forward end of zygoma and ' 
zygomatic plate standing farther out from skull. 
From Z. brunneus Thomas, Z. seorsus differs by its larger 
size, larger foot, and richer, more reddish coloration. 
Color and Pelage: Upper parts russet-brown, shaded with 
dull ferruginous, the latter color more intense on the rump; 
whole dorsal region thickly set with brownish-black-tipped 
hairs; sides paler, more yellowish; under parts dull buffy- 
gray, strongly shaded with dull ferruginous in anal region; 
line of demarcation between colors of upper and under parts 
indistinct ; upper surfaces of hands and feet yellowish-brown ; 
1 Seorsus, isolated, living apart. 
