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Show 1888.] MAMMALS FROM TEXAS. 449 In the skull the most marked difference, apart from its smaller size, is in the lesser development of the bullae, and the consequent increase of the space between them, as specially marked by the much greater breadth of the interparietal bones. These latter are very nearly as broad as long, while in all the specimens of D. agilis that I have seen their length is at least double and is often three times their breadth.' The muzzle also is rather shorter and slenderer, the front edge of tbe anterior zygoma-root starts out from it at a sharper angle, and the supraorbital margins are much more nearly parallel to one another, and less divergent posteriorly, than they are in D. agilis. In all these characters, both cranial and external, D. agilis compactus seems to stand on one side of D. agilis typicus exactly where D. deserti, Stephens \ does on the other, for just as D. compactus is distinguished by its smaller size, smaller bullae, and broader interparietal, so is D. deserti distinguished by its larger size, larger bullae, and narrower interparietal; the three forms apparently therefore represent three stages in one single series of development. 16. PEROGNATHUS FASCIATUS, Wied. a-j. 8 2, 12/85 and 4/86. Head and Forearm body. Tail. Hind foot, and hand. Ear, a. 8 96 98 22-2 26'5 6'3 b. 8 99 97 23 26-5 7-0 c. 8 90 90 227 26-6 6-1 d. 2 107 104 24-4 29 6-6 e. 2 99 99 22-9 27 6'5 /. 2 101 99 23-5 27 6-5 Mammae 1-2 = 6. "These pocket-mice are found all over the county, but individuals are scarce. They remain in their burrows during winter, but live a rather exposed life when grass and weeds cover the ground. They are strong and active, and the ones I had caged were very silent, but made a considerable fuss filling and emptying their pockets. I placed a heap of corn near their nest to see how fast they would remove it; I think a pair could move a peck one yard in six or seven hours. They appear to fight a good deal, as I often find them with scars and broken tails."-W. T. 17. CRICETODIPUS FLAVUS, Bd. a-e. 8 2 . 12/85 and 3 & 4/86. Head and Forearm and body. Tail. Hind foot. hand. Ear. a. 8 52 50 13*5 160 4-7 b. 8 51 48 14-2 16-3 5-2 c. 8 52 52 14-1 17 4-4 d. 8 51-5 52 137 16-4 4-5 1 Am. Nat. xxi. p. 42 (1887). The author unfortunately does not state whether his species has fou or five hind toes. |
