AGES OF MATURE. 411 



DESCRIPTION OF FIG. 387. 



1. Corbis corrugata, from the sand-rock, Atheriield: the figure is cne- 



half the size in linear dimensions of the original. 

 '2. Trigonia caudata, from the sand-rock, Atherfield. 

 3. Gervillia anceps, from the Cracker Rocks, Atherfield ; a denotes the 



markings of the hinge, which are seen in consequence of the valves 



being slightly displaced. It is represented half the size linear of the 



original. These shells are often much larger, and more elongated 



than in the figure. 

 nus striato-costata ; a small shell, common in the Cracker Rocks at 



Atherfield ; the figure is twice the size of the original in linear 



dimensions. 



5. Area Raulini, from the sand-rock, Atherfield. 



6. Perna Mulleti, from the lower beds of sand in conjunction with the 



Wealden, Sandown Bay ; the figure is but half the size of the origi- 

 nal : a, the structure of the hinge ; by comparing this figure with a, 

 No. 3, the difference of the hinge in the genera Perna and Gervillia 

 will be recognized. This large and remarkable shell is highly cha- 

 racteristic of the lower beds of the greensand. 



7. Venus parva, from Shanklin Cliff. 



DESCRIPTION OF FIG. 388. 



1. Thetis minor, from the ferruginous sand-rock at the base of Shanklin 



Cliff. 



2. Another view of the same, to show the beaks and hinge-line. 



3. Exogyra sinuata, represented one-fourth the natural size ; it is often 



found much larger. From the greensand at Shanklin, Ventnor, 

 Sandown, &c. 



4. Tornatella albensis, from the Cracker Rocks, Atherfield. 



5. Terebratula sella ; an abundant shell in the sand at Atherfield. 



6. Nucula scapha, from the sand-rock, Atherfield. 



The three followina shells are embedded in a fragment of the Cracker 

 Rock, from Atherfield. 



7. Natica rotundata. 



8. Pterocera retusa. 



9. Rostellaria RobinaldinL 



10. Cerithium turriculatum, from Atherfield. 



11. Ancyloceras gigas, from Atherfield. The figure is one-third the size, 



linear, of the original. This fossil is often found two feet in length, 

 associated with Ammonites equally gigantic. 



