PLATE 79. 
Fig. 1. 133. 7. Lingula quadrata. (Pag. 285.) 
1 a, b. Figures of two specimens, showing the difference ordinarily seen in the form of this fossil. 
1 c. A portion of the surface magnified. 
Fig. 2. 141. 4. Lept^ena alternata. (Pag- 286.) 
2 a. Mould of the interior of the convex valve of this species, showing the form of the visceral impression, 
the oblique teeth, etc. The nasute character is well preserved. 
2 b. Figure of a similar specimen, where the nasute character is less conspicuous. 
2 c. A smaller specimen of the same character, showing a slight contraction in front. 
2 d. A portion of the surface of one of these enlarged, showing the striato-punctate character. 
2 f. The impression made by the outside of the convex valve of this species, showing the fascicles of striae in 
a perfect manner. 
2/*. A cast of a large symmetrical specimen, showing the same characters of the surface, form of visceral 
impression, etc. 
2 g. A small specimen, preserving the shell, and showing the striae in interrupted fascicles. 
2 gf. A portion of the surface enlarged. 
2 h, i. Figures of specimens which still preserve a part of the shell, having the striae in broad fascicles of 
small ones separated by larger ones. 
2 k. Interior of the ventral valve, showing two small teeth on the hinge line, with three diverging callosities. 
2Mould of the interior of the ventral valve, showing the two cavities made by the teeth, and the impressions 
of the radiating callosities. 
Fig. 3. 146. 9. Lepttena sericea. (Pag- 287.) 
3 a. A mould of the interior of the shell. 
3 b. An enlarged portion, showing the striato-punctate character of the surface. 
3 a*. Another specimen, presenting more distinctly the usual character of casts of this species. 
Fig. 4. 155. 2. Orthis testudinaria. (Pag- 288.) 
4 a, b. Casts of the interior of the dorsal valve. 4 c. Cast of the interior of the ventral valve. 
4 d. A similar cast, more strongly impressed by the striae. 
4 e. A fragment of the impression of the outer side of the ventral valve, showing the fine concentric striae, 
which crenulate the diverging striae. 
Fig. 5. 341. 19. Orthis erratica. (Pag- 288 .) 
5 a, b. Dorsal and ventral views of the cast of a large specimen. 5 d. Ventral view of a small specimen. 
5 c. Front view of a larger specimen. 5 e. Cardinal view of a large specimen. 
5 f. Profile view of a moderately convex specimen. 
Fig. 5*. 342. 20 . Orthis centrilineata. (Pag- 289.) 
5 a*. A specimen, natural size. 5 b*. Magnified portion of the cardinal line and visceral impression. 
5 c*. Several striae enlarged, showing the bifid and trifid character. 
Fig- 
6 . 
186. 19. 
Atrypa increbescens. 
(Pag. 289.) 
Fig. 
7. 
343. 5. 
Orbicula? subtruncata. 
(Pag. 290.) 
7 a. A small fragment with several 
individuals upon the surface. 
7 b. A single specimen enlarged. 
Fig. 
8 a. 
344. 6. 
Orbicula? crassa. 
(Pag. 290.) 
Fig. 9. 345. 7. Orbicula c^elata. (Pag. 290.) 
9 a. An imperfect specimen. 9 b. The same enlarged, to show the central depression and lateral plications. 
9 c. A portion of the surface still farther enlarged, showing the character and arrangement of the papillae. 
