1893.] MR. O. THOMAS ON MAMMALS FROM CENTRAL PERTT. 337 



Skull — basal length 17 ; greatest length 20'8 ; zygomatic breadth 

 12 ; intertemporal breadth 5-6 ; palate, length 9-5, breadth outside 

 5^ 8-6, inside ^ 4-4 ; front of canine to back of jii^ 6-5 ; ditto in 

 lower jaw 6-9 ; horizontal length of m^ 2-0, 'm- 1"8, ^ 0-4. 



There is no necessity for any comparison of this species with 

 its allies, as its dental formula distinguishes it at once from all 

 except the A. i^ierspicillaius group, of which the smallest member 

 is of at least three or four times its bulk. 



A. glaucus is perhaps Tschudi's " PlujUostoma pusillum, Natt." \ 

 but has clearly nothing to do with batterer's species, which was 

 placed by Dobson in the genus Chiroderma, and later on transferred 

 by myself to Vampyrojjs'^ . 



11. SCITJRUS TARIABILIS, Geoff. 



a. Ad. sk. (S . Chanchamayo. 



12. SCIURUS CHRTSURUS, Puch. 



a. Ad. sk. c? • La Gloria, Chanchamayo. 



13. Ehithrodon pictus, Thos. 



a. Ad. sk. San Bias, Cordilleras, 18000 feet. 30/4/90. 



14. IcHTHTOMTS STOLZMANNi, g. & sp. nn. (Plate XXVIII. and 

 Plate XXIX. figs. 1-6.) 



ICHTHTOMYS, g. n. 



Form modified for an aquatic pisci^'orous life. 



Head markedly depressed, so as to give its side Aiew a resemblance 

 to that of a snake. Eyes and ears small. Whiskers long, stout, 

 and prominent. Pur short and close. Hind feet (Plate XXIX. 

 fig. 5) very broad; toes partially webbed, broadly and closely 

 ciliated on each side ; their soles, naked, with five broad low pads. 

 Tail long, cyluidrical, but increased in height vertically by ha^'ing 

 its under surface clothed with short elongated bristles. 



Cajcum (fig. 6) much reduced in volume, very short, and only 

 of the same diameter as the rectum. Small intestine of medium 

 length ; colon and rectum proportionally short. 



Skull (figs. 1-4) curiously like that oi Hydromys, its dorsal outline 

 concave over the orbits, flattened and depressed throughout. Supra- 

 orbital edges smoothly rounded, without any trace of ridges ; supra- 

 orbital foramina proportionally large, not within the orbit, but upon 

 the top of the interorbital space. Infraorbital foramen exactly as 

 in Hydromys, as broad below as above ; anterior zygoma-root 

 very short horizontally, its anterior edge vertical, not projecting 

 forwards. Zygomata extraordinarily weak, not properly ossified 

 at the junction of the malar with the maxillary process. Palatine 

 foramina of medium length. 



Teeth. Incisors with their front surfaces so turned in towards 



1 Faun. Peruana, p. 63 (1844). 



^ Ann. Mag. N. H. (6) iv. p. 170 (1889). 



