142 



pital posteriorly and laterally as far as the zygomatic arch, which 

 is by no means the case in the AUactagas, where all the osseous parts 

 of the ear are of moderate dimensions. Another differential character 

 between the two genera, is presented by the maxillary arch, which 

 circumscribes externally the suborbital foramina, and wliich, in the 

 AUactagas, may be said to be linear, and presenting a very limited 

 surface for the attachment of muscles. Lastly, we may note a dif- 

 ference in the relative development of the jaws, the lower being com- 

 paratively much shorter in the AUactagas than in the Jerboas." 



The author then proceeds to describe a new species of Allactaga, 

 a native of Barbary, for which he proposes the name of A . arundinis. 

 Its length from the origin of the tail to the end of the muzzle, 5 inches ; 

 length of the tail, 5 inches and 2 or 3 lines; of the ears, 1 inch; length 

 of the tarsi from the heel to the extremity of the toes, 22 lines. AU 

 the upper parts of the body are of a beautiful greyish yellow, with 

 yellowish sides and tail of the same colour, terminated by a tuft of a 

 blackish brown at its origin, and white at the extremity. The sides 

 of the cheek, the ventral surface of the body, and tlie internal limbs 

 are white ; large brovv'u moustaches adorn the sides of the muzzle. 

 The incisors are white and entire, the eai's almost naked. 



M. Cuvier next proceeds to consider the characters and affinities 

 of the genera Gerbillus and Mei'iones, and enters into a critical ex- 

 amination of all the species referred to that group. To these he adds 

 another species, the habits of which he details, and describes at length 

 under the name of G. Burtoni. The species which he thus includes 

 are, 1st, G. Egypt iacus, syn. Dipus Gerbillus, Meriones quadrima- 

 cw/a/M5, Ehrenberg ; 2nd, Gerbillus pyramidum, syn. Dipus pyramidum 

 Geoff., Meriones robustus Rupp. ; 3rd, G.pygargiis, syn. Meriones 

 Gerbillus, Rupp. ; 4th, G. Nidicus, syn. Dipus Nidicus, Hardwicke ; 

 5th, G. Africanus, syn. Meriones S c hi eg e I ii Snwitz., G. Afra Gray; 

 6th, G. brevi-caudatus ; 7th, G. Otaria ; 8th, G. Burtoni. Theautlior 

 enters into detailed descriptions of each of these species from original 

 specimens. M. Cuvier lastly considers the affinities of the Gerbillus 

 and AUactagas to the Gerboas, and concludes that the Gerbillus have 

 a much nearer affinity to the Muridte. 



Mr. Gould exhibited to the Meeting all the species from ■which the 

 drawings had been taken for the first part of his new work on the 

 Birds of Australia, among which were several new and very remark- 

 able forms. The following hitherto undescribed genera and species 

 were named and characterized. 



OcYPTERUs suPERCiLiosus. Oc.facle, guld, pectoreque nigrescenti- 

 griseis ; lined superciliari alba ad basi7i rostri excurrente ; summo 

 cupite, corpore superiore alisque fuliginosis ; abdomine crissoque 

 castaneis ; rectricibus griseo-fuliginosis, ad apicem ulbescentihus, 

 intermediis duabus exceptis ; rostro plumbeo, ud apicem nigra ; 

 pedibus plumbeis. 



Long. tot. 7 unc; rostri, 1 ; ala, 4J; caudte, 3 ; tarsi, |. 



Hah. In NovS Cambria Australi. 



