1862.] 



KIRZBT FOSSIL CHITONS. 



235 



The posterior plate resembles that of many recent Chitons ; it is 

 wider than long, has a semicircular posterior margin, an anterior 

 margin obtusely angulate, a depressed apex almost centrally placed ; 

 shell strong, and its surface marked by a few coarse lines of growth. 



Figs. 3-6. — Plates of Chiton coloratus. 



(Nearly twice natural size.) 



3. Intermediate plate. 



4. Lateral view of the same. 



5. Posterior plate, 



6. Lateral view of the same. 



The intermediate plate possesses considerable interest on account 

 of its colour-marking ; the colour is very evident ; the uncoloured 

 surface is grey, which is the tint of the matrix. That this is truly 

 the remains of the original colour I can scarcely doubt, considering 

 the s}Tnmetry observed in its arrangement, which cannot be ascribed 

 to the accidents of fossihzation. 



Both plates belong to the ordinary type of Chiton. The interme- 

 diate plate, from its comparatively great median length, is probably the 

 second, or perhaps the penultimate, of the series. C. gemmatus, De 

 Kon., perhaps approaches the nearest to this species among the fossil 

 forms, particularly in the general outline of its intermediate plates. 



3. Chiton ? Spec. nov. Figs. 7 & 8. 



A shield-shaped plate, much wider behind than before, strongly 

 keeled medianally, sloping rapidly on each 

 side and anteriorly ; apex prominent, point- 

 ed, and slightly depressed ; two faint lines 

 diverge from the apex to the antero -lateral 

 margin, being apparently analogous to the 

 lateral sulcations that bound the dorsal areas 

 of many Chitons ; lateral areas evident, 

 small ; surface rather coarsely granulated, 

 granulations arranged somewhat concen- 

 trically after the manner of the lines of 

 growth; lines of growth faintly marked, 

 regular; shell rather strong ; length ^ inch, 

 breadth -^ inch. 



The only plate known to me that has 



Figs. 7 & 8.— Plate oj 

 Chiton? 

 (Enlarged one-third.) 

 7 



Upper view. 

 Lateral view. 



