PLATE 30. 



Fig. 1. 130. 4. LiNGULA ATTENUATA? (Pag. 94.) 



I (I, IS the largest individual ol' this species yet seen. 1 b. A specimen ol the oidinarv size. 



Fig. 2 a, b, C. 131. 5. LiNGULA RICINIFORMIS. (Pag. 95.) 



Fig. 3 a, A. 132. 6. Lingula jeq.uai,is {a variety of the /ast species?). (Pag. 95.) 



Fig. 4. 133. 7. Lingula quadrata. (Pag- 96.) 



4 a. A specimen of the ordinary size ; the shell partially e.xlbliated, and presenting the strong radiating striae 



along the centre. 

 4 b. View of the edge of the shell, with the two valves clo.sed. It appears slightly inequivalve from compression. 



4 c. A specimen of larger dimensions, from which the shell is partially exfoliated. 



Fig. 5. 134. 8. LiNGULA elongata. (Pag- 97.) 



Fig. 6. 135. 9. LiNGULA curta. (Pag. 97.) 



fi a. Specimen from the Utica slate. 6 b. Specimen from the Trenton limestone. 



Fig. 7. 136. 10. LiNGULA obtusa. (Pag. 98.) 



7 a. A very perfect specimen of large size, giving the e.xact form of the shell : radiating striiE scarcely visible. 

 7 b. Another specimen, the form not quite so perfect as the last, but the radiating striae more distinctly visible. 



7 e. A smaller individual of the same species. 



Fig. 8. 137. 11. LiNGULA ceassa. (Pag. 98.) 



8 a, b. View of both valves of this species. 



5 c. View of the edge of both valves, closed ; one being more convex than the other, and slightly arched. 

 S d. A larger specimen, somewliat crushed. S e. A smaller specimen. 



Fig. 9. 138. 2. Orbicula? FiLosA. (Pag. 99.) 



y a. A young shell, very convex or obtusely conical in form. 



9 b. A larger shell, less convex than the last : this portion is magnified. 



9 e & d. Two apparently full grown shells of this species; the form is much depressed, nearly flat, and the 

 surface completely covered by fine striae. 



Fig. 10. 139. 3. Okbicula lamellosa. (Pag. 99.) 



10 a. Ventr.d view. lu *. Lateral view. 



Fig. 11. 140. 4. Orbicula terminalis. (Pag- 100.) 



11 a. Dorsal valve, showing the central apex and lateral depression, which extends to the margin. 

 1 1 A. Ventral valve with marginal apex. 1 1 c. Lateral view of a perfect specimen. 



U d. Ventral valve, marked with strong concentric lamellae; apex marginal. 



