242 CATALOGUE OF THE FOSSILS OF THE PERMIAN SYSTEM 
Orpver. SCUTIBRANCHIATA, Cuvier. 
Faminy. CALYPTRHIDA, Gray. 
13. CALYPTRAMA, Lamarck. 
1. C. ANTIQUA, 2. s. 
Shell small, patelliform ; strongly ribbed longitudinally ; 
margin crenulated ; two deep furrows internally, from the 
apex to the margin, corresponding with two strong ribs on 
the outer surface. 
In Magnesian-limestone ; rare. Tunstall-hill. 
Only one small specimen of this shell has occurred. The cha- 
racters noted above are very conspicuous, and its strong resem- 
blance to many of the Calyptrea has induced us to place it in 
that genus. 
Orper. CYCLOBRANCHIATA, Cuvier. 
Faminy. Curronipz, D’Orbigny. 
14, CHITON, Linneus. 
Chiton, Ann. Nat. Hist., vol. xiv.; London Geol. Journal, 
1846, p. 10. 
In the Magnesian-limestone; rare. Tunstall, Humbleton, 
Silksworth. 
Plates of a Chiton were first discovered in the limestone of 
Tunstall-hill, by W. K. Loftus, Esq., of Newcastle, in company 
with Mr. W. King. We have since taken specimens at Humble- 
ton and Silksworth. The plates have, hitherto, been found se- 
parate, but not far distant from each other. Figures of the 
plates of this Chiton are given in the London Geological Jour- 
nal, by Mr. W. King. 
