33 



cing but little, the symphysis elongated, and the obturator foramen 

 of large size. The femur is straight, strong and smooth, and mea- 

 sures 1 inch T Vths ; the tibia 2 inches Aths ; the Jibula is complete 

 and forms the external malleolus ; from the os calcis to the end 

 of the longest toe 2 inches T vth; the toes four in number, of which 

 the outer one is the shortest, the third from the outside the longest, 

 the second and fourth equal. 



" In the published observations before referred to I stated that 

 the Chinchilla appeared to be closely allied to Mr. Brookes's new 

 genus Lagostomus, and the character of the skeleton of the Chin- 

 chilla compared with the figure and description of Lagostomus in 

 the 1st part of the 16th volume of the * Transactions of the Lin- 

 nean Society' confirms the general similarity. Still, the more 

 complicated structure of the teeth, and the existence of an additi- 

 onal toe on each of the feet, require for the Chinchilla the generic 

 distinction claimed for it by Mr. Bennett and by Mr. Gray. 



" The resemblance of the skeleton of the Chinchilla to that of 

 the Jerboa is also remarkable, particularly in the form of the head, 

 in the excessive development of the auditory cavities, and the 

 small size of the anterior extremities compared with the hind legs." 



Mr. Yarrell having concluded the reading of his Notes, it was 

 remarked that MM. Isidore Geoffroy- Saint- Hilaire and Dessalines 

 d'Orbigny had proposed, in the * Annales des Sciences Naturelles' 

 for November 1830, the creation of a new genus, Callomys, to in- 

 clude the Chinchilla and the Viscaccia. The latter animal is the 

 Dipus maximus, De Bl., and consequently the type of the genus 

 Lagostomus, described by Mr. Brookes in a paper read before the 

 Linnean Society in 1828, and published in the Transactions of that 

 body in 1829, in which the system of dentition and the osteology 

 are treated of in detail. The Chinchilla, long known in commerce 

 but only recently made known to science, was described as the type 

 of a distinct genus, under its common name, by Mr. Bennett in 

 1829, and by Mr. Gray in August 1830: its true characters seem 

 even now to be unknown to the French authors above referred to, 

 who appear to be acquainted with its skin alone, and never to have 

 examined either its teeth or the number of its toes. In these re- 

 spects it deviates from the characters of their proposed genus ; a 

 genus which cannot be adopted, inasmuch as it is composed of 

 heterogeneous materials, and as the two types included in it have 

 both previously been described and designated as distinct groups. 



Specimens were exhibited of the trachece of various Gallinaceous 

 Birds included in the genera Pauxi, Crax and Penelope of M. Tem- 

 minck $ and Mr. Yarrell observed that these birds have each, as 

 far as they have yet been examined, been found to possess a spe- 

 cific difference in their organs of voice. Among the trachece placed 

 on the table was that of the Red-knobbed Curassom, Crax Yarrellii, 

 Benn., a new species lately described from the Society's Menagerie, 

 and which had recently died. The trachea of this species differs 

 from all those previously known, but most resembles that of the 



