ON THE PERMIAN CHITONID^. 243 



tella or Calyptrcea than the postal plate of C. Hancockianus, or any 

 of the plates of C. antiqua ? all of which would very probably 

 have been referred to one of these genera, had it not been for the 

 peculiar matrix in which they occurred allowing of the full ex- 

 posure of their delicate processes of insertion. The existence of 

 Permian Chitonelli with plates simulating the shells of the Patel- 

 li'dce ought to induce great care in the determination of Patelli- 

 form fossils; and, in every instance where it is possible, the 

 extreme margin should be worked out, to prove whether it be 

 produced into a process of insertion or not ; for, unless this is 

 done, or the muscular impressions known, great doubt must 

 certainly exist as to the genera to which they truly belong. 



FAMILY CHITONID.E. 



Genus CHITON, LinncBUS. 

 1. C. LoFTUSiANus, King. Plate XIIL, figs. 31-41. 



Chiton, Ivmg, 1844, Ann. Nat. Hist., vol. xiv., p. 

 382; King, 1846, Charlesworth's Lond. Geol, 

 Journ., vol. i., p. 10; Howse, 1848, Catal. Perm. 

 Foss., p. 24. 

 Chiton Lojiusianus, King, 1848, Catal. Organ. Rem. 

 Perm. Rocks, p. 12; King, 1850, Monog. Perm. 

 Foss., p. 202, pi. 16., figs. 9-14; Howse, 1857, 

 Ann. Nat. Hist., 2. ser., vol. xix., p. 463. 

 General outline elongated oval ; plates thick, finely granulate. 

 Anterior plate nearly semicircular, posterior margin rather re-en- 

 teringly angulate, with an elevated apex. Second plate transverse, 

 though comparatively long medianly ; more acuminated laterally 

 towards the extremities ; posterior margin oblique, slightly con- 

 cave, much produce near the apex; anterior margin almost 

 straight, but slightly sinuate laterally ; in other respects like the 

 succeeding plates. The succeeding, or rather intermediate plates, 

 very transverse, rather acutely angulate medianly, directed ante- 

 riorly, and slightly tapering near the extremities ; median line 



