98 MR. O. THOMAS ON RODENTS FROM PERTJ. [Jan. 17, 



differ but little from those of a bird. Notwithstanding the massive- 

 ness of the skull, nearly every suture is persistent; in the light 

 skull of the Bird nearly every suture is obliterated. 



" The pier of the mandible explains, and is explained by, that of 

 the Lizard on one side, and the Salamandrian below. The jaw itself 

 is at au early period quite continuous with the hyoid arch ; and that 

 arch is for a time continuous with the auditory columella, as in the 

 Hatteria of New Zealand ; and the columella itself is only a modi- 

 fied part of that arch. In its early segmented state, however, and 

 in its later broken-up condition, it comes very near to what is found 

 in the mammal, and greatly helps the morphologist in working out 

 a harmony between this arch in the Sauropsida and the Mam- 

 malia. 



" In the discussion which took place a dozen years ago between 

 Professors Peters and Huxley (for the views of the latter see P. Z. S. 

 1869, pp. 391-407), as to the early continuity of the mandibular and 

 hyoid arches and their nature, both combatants were right and both 

 were wrong. The two arches are continuous for a time ; but that 

 condition does not sustain Prof. Peters's reasoning. The deductions 

 of Prof. Huxley, in spite of the fact that he worked with imperfect 

 materials, will remain true for all time." 



Prof. Parker's memoir will be published entire in the Society's 

 Transactions.' 



The following papers were read : — 



1. On a Collectiou of E,odents from North Peru. By 

 Oldfield Thomas^ F.Z.S., British Museum. 



[Received December 15, 1881.] 

 (Plate IV.) 



The collection now described was obtained by M. Stolzmann, the 

 well-known Polish collector, iu Northern Peru, and has been placed 

 in my hands for determination by Prof. Taczanowski, of the Warsaw 

 Museum, by whom a nearly complete set has been presented to the 

 British Museum. 



Every specimen has its exact locality, date, and altitude recorded ; 

 and the habits of many of the species have been noted by M. Stolz- 

 mann, whose remarks, placed between quotation-marks, are appended 

 to their respective species. 



The localities from which the collection was obtained are as 

 follows : — 



Tumbez, — Capital of the province of the same name. Situated on 

 the river Tumbez, at about 4 miles from its outlet in the Bay of 

 Guayaquil (3° S. lat.). 



Tambillo. — A colony on the river Malleta, a tributary of the 

 Upper Amazons. This river forms the boundary between the pro- 



