386 



2135. The skull of a mature Canada Porcupine (Hystrix dorsata), with the pre- 

 molars in use and in place. Most of the cranial sutures are obliterated. 



Presented by Sir John Richardson, M.D., F.R.8. 



Genus Atherura. 



2136. The skull of the Indian Brush-tailed Porcupine (Atherura fasciculata). 



The last true molar is not iu place ; the milk-molar is not shed. The interparietal has 

 coalesced with the superoccipital, and extends forwards to penetrate the frontal suture, com- 

 pletely separating the parietal bones from each other, as in most fishes. The parietal bones 

 have coalesced with the anterior part of the squamosals, the posterior or clamping processes 

 remaining distinct : the tympano-petromastoid is loosely suspended beneath them. The 

 nasal bones are parallelograms, not extending further back than the base of the antero- 

 inferior root of the zygoma. The premaxillaries send backwards their contracted but ob- 

 liquely truncated extremities to the same extent. The antero-inferior is still separated from 

 the antero-superior process of the maxillary by a suture : they circumscribe very wide ant- 

 orbital vacuities. The bony palate terminates by a thick rounded concave border behind the 

 second true molar tooth (m 2), which is the third of the grinders here in use. 



Presented by Sir Stamford Raffles, P.Z.8. 

 The following are parts of the same skeleton of the Atherura fasciculata : 



2137. The atlas. 



This vertebra differs from that of the Erithizon dorsatum by the presence of a ridge 

 extending transversely over the neural arch, so as to define an anterior and posterior surface 

 on the upper part of that arch. 



2138. The axis. 



It has a long neural spine, but is distinct from the third vertebra. 



2139. The five succeeding cervical vertebrae. 



2140. Nine anterior dorsal vertebrae. 2141. Four posterior dorsal vertebrae. 

 2142. The five lumbar vertebrae. 2143. The three sacral vertebrae. 

 2144. Three of the caudal vertebrae. 2145. The right scapula. 



