OCR Text |
Show 524 MR. OLDFIELD THOMAS ON [Dec. 12, When the difficult Mus musculus group comes to be worked out these specimens will be of the greatest value, but they cannot well be determined at present. No. 55 is a typical dark longtailed house-mouse ; the others are pale desert forms. 19. M icrom ys m y s t a c in u s Danf. & Alst. cf. 64, 65, 66. 5 . 67. Sumela, 30 mi. S. of Trebizond. 1500'. " Trapped on hill-side below the fir-woods."-R. B. W. 20. M icrom ys s y l v a t ic u s a r ia n u s Blanf. cf. 30, 34. $ • 32. Bachtiari Mts., 100 mi. N.E. of Ahwaz. 5800'. These specimens are coloured very like the South Persian M. s. witherbyi Thos., but have the larger teeth of arianus. 21. C alom y scu s b a ilw a r d 1 Thos. (Plate XYI.) Abstr. P. Z. S. No. 24, p. 23, Dec. 19, 1905. 25. cf • Mala-i-Mir, 70 mi. N.E. of Ahwaz. 4300'. 10 April, 1905. B.M. No. 5.10.4.68. Type. C a lom y scu s . A member of the Cricetince, or biserial-tootlied Muridse, of which the only recent Old World * members hitherto known have been the Cricetus group and the South African Mystromys. Most nearly allied to the N. American Peromyscus, with which it shares the possession of only five cusps on the anterior upper molars. External form as in Peromyscus, but the tail bushy terminally, as in many Gerbilles, to which the pallid colour also gives a resemblance. Ears large. Fur soft. Feet of normal length and structure ; soles naked except just under the heels ; sole-pads six, the posterior one far back, separated from the others. Tail long, pencilled, the single specimen with a peculiar double tuft of white hairs at a point two-thirds along it, which may indicate the presence of a special gland, or, more probably, be merely due to an accidental injury. Skull, as compared with that of Peromyscus, low, flat, and rounded, the shape of the brain-case recalling that of a dormouse. Bullae low, little developed. Palatal foramina comparatively small. Coronoid process of mandible long, considerably overtopping the condyle. Incisors smooth. Molars brachyodont, thin, pattern very similar to that found in Peromyscus, but even more simple; the cusps low, and the valleys between them shallow, and without any trace of supplementary intermediate ridges. First upper molar with only five cusps and without any trace of that duplication of the anterior cusp so characteristic of Cricetus and its allies. # Madagascar excepted. |