688 



4334. The skull of the American Cross Fox (Canis decussatus). 



It appears to be only a large and powerful variety of the Common Fox. 



Presented by Sir John Richardson, M.D. 



4335. The skull of the Isatis, or Arctic Fox (Canis lagopus). 



It agrees in size with that of the specimen No. 4329, but has a shorter facial portion, and 

 the maxillary bones articulate with a smaller proportion of the nasals. The dental system is 

 complete and resembles that of the Common Fox. 



Presented by Henry Cline, Esq. 



4336. The skull, wanting the lower jaw, of a not full-grown Isatis (Canis lagopw). 



The squamosal has been removed from the right side, showing the portion of the cranial 



cavity which it protects. 



Mus. Brookes. 



The following, to No. 4357 inclusive, are parts of the same skeleton of a female Isatis (Ca- 

 nis lagopus) : 



Hunterian. 



4337. The vertically and longitudinally bisected cranium. 



4338. The lower jaw. 



4339. The atlas. 



The transverse process is perforated obliquely and notched anteriorly by the vertebral 

 artery before it pierces the neural arch. 



4340. The axis. 4341. The five following cervical vertebrae. 



4342. An anterior dorsal vertebra. 



4343. The tenth and eleventh dorsal vertebrae. 



They show well the distinction between the diapophyses and the anapophyses. 



4344. The first and second lumbar vertebrae. 



The diapophyses are here elongated by the connate pleurapophyses. The anapophyses are 

 marked a. 



