1868.] DR. J. E. GRAY ON SACCOMYINjE. 203 



1. Cricetodipus flavus, S. Baird. 



Peroynathus flavus, Spencer Baird, Proc. A. N. Philad. vii. 1855, 

 p. 332 ; Mamiii. N. A. 423, t. 21. f. 3 (head). 

 Hub. Nebraska, Ulah, Texas, Sonora. 



2. Cricetodipus parvus, Peale, Mamm. & Birds U. S. Expl. 

 Exped. 1838, p. 53. 



Perognathus parvus, Leconte, Pr. Acad. N. S. Philad. vi. 1853, 

 p. 235 ? 



P. cricetodipus parvus, Aud. & Bachm. N. A. Quad, iii, 328, 1854 ; 

 Spencer Baird, Mamm. N. A. 425 ? 



Hab. ? 



A doubtful species. 



tt Vpper cutting-teeth broad and smooth in front. 



5. Heteromys, Gray. 



Cutting-teeth smooth in front, the upper flat, square in front, 

 lower compressed, narrow in front. Fur formed of flat, channelled, 

 tapering spines. Pouches covered with hair. Tail slender, taper- 

 ing, covered with rings of square smooth scales, with rings of short 

 distant smooth hairs from the suture between the rings of the scales 

 and about twice as long as the scales. 



Hetercmys, Gray, Spic. Zool. i. 10 (1831). 



** Fur consisting of uniform rather short broad spines tapering to a 

 point, and with a broad central channel on the upper surface, 

 with some scattered, slender, elongated hairs. 



1. Heteromys anomalus. B.M. 



Fur pale chestnut-brown, white beneath. 



Mus anomalus, Thompson, Linn. Trans, xi. 151, t. 10. 



Heteromys anomalus, Gray, Spic. Zool. i. 10 ; Less. Mamm. B. M. 

 120, 1843. 



Heteromys thompsoni, Lesson. 



Basynotus anomalus, Wagler. 



Cricetus anomalus, Desm. Mamm. 513. 



Hab. Trinidad {John V. Thompson). Type, B.M. 



Confounded with Loncheres myosurus, Licht. ; M. leptosoma, 

 Licht. See Lonchura anomala, Kuhl, Beitr. 70. 



Mr. John Vaughan Thompson was a very careful and accurate 

 observer, and far in advance of his time. He discovered the structure 

 of Polyzoa, the transformation of Crustacea and of the Cirripedes, 

 the larva state of Comatula, and the transformation of Mollusca. 

 He sent a paper on the latter subject, with others, to the Royal 

 Society ; but they were not understood or estimated ; and instead of 

 being printed in the ' Transactions,' they were placed in the Ar- 



