1895.] Zoology. 171 
Mexican Glires.—In studying the series of Mexican Rodents col- 
lected by Mr. E. W. Nelson, Dr. C. H. Merriam finds that a wood rat 
described by him sometime ago under the name Neotoma alleni repre- 
sents a new genus for which he proposes the name Hodomys. ‘This 
genus is characterized by having the crown of the last molar shaped 
like the letter S, and also by important cranial distinctions. 
Associated with Hodomys, by reason of dental characters are Ptysso- 
phorus, Tretomys (both fossil) Xenomys and Neotoma. These five 
genera form a group presenting, according to Dr. Merriam, nearly 
every important step in the evolution of the modern genus Neotoma 
from the Cricetine series, Ptyssophorus is the more primitive type; 
Tretomys and Hodomys seem to represent more advanced stages in the 
evolution of the group, while Xenomys and Neotoma are more special- 
ized. 
The five genera above enumerated are classed together by the author, 
as a subfamily, the Neotominae, and it seems to be an independent off- 
shoot, as is also the Arvicolinae, from the half-tuberculate crowned 
Cricetinae. 
Dr. Merriam redefines the genera Ptyssophorus and Tretomys, and 
characterizes the new genus Hodomys with reference to the more 
specialized genera Xenomys and Neotoma, and adds descriptions of all 
the known species. (Proceeds. Phila. Acad. Nat. Sci., Sept., 1894.) 
Zoological News,—Spongiz.—lIn a paper on the anatomy and 
relationships of Lelapia australis, Mr. Arthur Dendy calls attention to 
the peculiar reticulated fibrous character of the skeleton, which has pre- 
viously escaped notice. This character is unknown in any other living 
calcareous sponge, while it forms a prominent feature in the fossil group 
Pharetrones of Zittel. The author accordingly regards Lelapia aus- 
tralis as a living representative of Pharetrones which family must now 
be classed with recent Calcarea. (Quart. Journ. Micros. Sci. June, 
1894.) 
Pisces.—A new species of Ribbon Fish, Trachypterus rex-salmono- 
rum is described and figured by Dr. Jordan and Prof. Gilbert. Accord- 
ing to the authors, this species bears some resemblance to L. altivelis 
described by Kner from Valparaiso. ‘The latter species has, however, 
the nuchal crest much lower and farther back, the first dorsal and the 
ventrals much lower, the second dorsal fin higher, the skin rougher, 
the four black spots different in size and position from those found in 
T. rex-salmonorum, and the caudal rays divided near the base. 
