Cartridge Buff). This pale
specimen is from the north side of the inlet. The brownish stripe on the
ventral side of the tail is absent on the distal two-fifths of the tail
and the specimens are uniform in this respect. On the occlusal surfaces
of the cheek-teeth, the enamel surrounding the dentine is incomplete on
both the lingual and labial sides of the teeth of five individuals and
is incomplete on the labial side of some of the teeth of a sixth
specimen.

In the snap traps, all of which were baited with rolled oats, more than
twice as many land crabs as kangaroo rats were taken. Judging from
tracks in the sand, land crabs greatly outnumbered kangaroo rats. The
parietal bones in two of the 13 skulls are much eroded by some parasite
(seemingly nematode worms) and in one of these two specimens the roof of
the left tympanic cavity is perforated. As regards life-zones, the
occurrence of _Dipodomys ordii_ in the lower part of the Lower Sonoran
Life-zone on the off-shore beach 88 and 90 miles south of Matamoros is
low zonally and perhaps is at or near the zonal margin of the range of
the species. The crabs and worms conceivably are two of the
environmental features inhospitable to the rats.

_Specimens examined._--Total, 14, all from Tamaulipas, Mexico, as
follows: 88 mi. S and 10 mi. W Matamoros, 7; 90 mi. S and 10 mi. W
Matamoros, 7.

When Setzer (Univ. Kansas Publ., Mus. Nat. Hist., 1:473-573, December
27, 1949) reviewed the subspecies of _Dipodomys ordii_ he lacked
specimens of _Dipodomys ordii compactus_ from the type locality or from
anywhere else on Padre Island. He used as representative of _D. o.
compactus_ specimens from Mustang Island, Texas, the island next
northeast of Padre Island. Through the courtesy of Mr. Stanley P. Young,
Dr. Hartley H.T. Jackson and Miss Viola S. Schantz, of the United
States Biological Surveys Collection, I have examined topotypes of _D.
o. compactus_ from Padre Island. This examination discloses that the
kangaroo rats on Padre Island and Mustang Island are significantly
different. Those from Mustang Island may be named and described as
follows:

MEASUREMENTS (IN MILLIMETERS) OF ADULT MALES OF FOUR SUBSPECIES OF
DIPODOMYS ORDII

Key:
A Total length F Breadth across maxillary arches
B Length of tail G Width of rostrum
C Length of hind foot H Length of nasals
D Greatest length of skull I Least interorbita