PLATE 80. 
Fig. 1. 346. 3. Avicula insueta. (Pag. 291.) 
1 a. A specimen, natural size. 1 b. A portion of the surface enlarged. 
Fig. 2. 347. 4. Avicula demissa. (Pag- 292.) 
2 a. A large perfect specimen, which is more elevated than usual. 
2 b. The impression of a smaller specimen in sandstone. 
Fig. 3. 348. 5. Avicula? desquamata. (Pag- 292.) 
3 a. A specimen, natural size. 3 b. An enlarged portion of the surface. 
Fig. 4. 349. 7. Ambonychia radiata. (Pag. 292.) 
4 a, b. The right and left valves of different specimens of this species. 
4 c. A smaller individual, with the radii distinctly marked, and more than thirty in number. 
4 d. A young specimen, with the radii finely marked. 4 e. A portion of the surface enlarged. 
4 /. A cast of the interior of the right valve : the posterior slope shows a straight, well defined, impressed 
line. 
4 h. Profile view of a specimen preserving both valves. 
4 i. Lateral view of the same. The difference in form between this and the preceding specimens is due to 
pressure. 
4 j. A large specimen incrusted at its base with a coral, of which an enlarged portion is given in 4 g. (The 
letter is omitted on some of the plates.) 
4 k. Enlarged portion of the surface, showing the same structure as 4 e. 
4 1. An impression of a part of the valve of a very large and strongly ribbed specimen. 
Fig. 5. 350. 8. Ambonychia carinata. (Pag. 294.) 
5 a. Left valve of this species. 
5 b. Profile view, showing both valves. The apparent inequality of the beaks is produced by a slight displace¬ 
ment from pressure. 
