PLATE 31 A. 
1. 141. 4. Lept^ena alternata. (Pag. 102.) 
X a. A specimen which is contracted just below the ears and bent abruptly upwards, having towards the front 
several folds, and a more prominent one directly in front. 
1 b. A lateral view of the same specimen, showing the abrupt and extreme deflection of the shell. 
1 c. A specimen having the same general form as the last, but contracted and folded in front so as to present 
precisely the same form as the Strophomena nasuta of Conrad. 
In both the preceding specimens the beak is perforated, as is exhibited in the enlarged view of the 
hinge in 1 a, which at the same time shows the foramen not quite closed. 
The nasute feature above indicated is often connected with a single elevated ridge, or more prominent 
stria, much larger than the others, and extending from the base to the beak of the shell. This appears 
very distinctly in the two preceding specimens ; but to prove that this character is common to the 
species, the specimen l is represented, showing a prominent line down the centre, while the shell is 
totally destitute of the other characters of S. nasuta , being scarcely convex and very regularly semioval. 
1 e,f,g&h. These figures represent a series of the younger shells of this species, as they occur in the com¬ 
pact limestone of Middleville, Little-Falls, Trenton-Falls, and other places. 
1 i. A very convex specimen, much contracted below the cardinal line, with the alternating striee less distinct. 
2. 142. 5. Lept^na camerata. (Pag. 106.) 
2 a. Lateral view of the specimen, showing the extreme concavity of the shell in the centre, and the nearly 
flat disc. 
2 b. Front view, showing the great deflection ; the surface is puncto-striat.e, from being denuded of the shell. 
3. 143. 6. LeptjENA deltoidea. (Pag. 106.) 
3 a. A specimen showing but a slight difference from the last described species. It is marked by distinct con¬ 
centric wrinkles upon the disc ; is finely striated, with more prominent elevated ones alternating with 
every four, five or six of the smaller ones. In this respect it partakes of the characters of specimen 1 i. 
3 6. A specimen presenting the same form as the last, except that it is more produced in front. The concentric 
wrinkles on the front are perhaps more distinct, and the shell is contracted more abruptly just below 
the extremities of the cardinal line, producing small acute ears. 
3 c. Lateral view, showing the elevation of the shell. 
3 d. A specimen of nearly the same form as the last. The concentric wrinkles are more distinct, and the ra¬ 
diating strise are equal, except on the central part of the shell, where they are stronger. 
3 e. A larger specimen, with the disc distinctly wrinkled and marked by nearly equal radiating striae; scarcely 
produced in front. The striae on the centre are more distinct than at the sides. 
3 /. A very perfect specimen in form and markings, from a drawing by Mr. Conrad. 
4. 144. 7. Lepta;na tenuistriata. (Pag. 108.) 
4 a. A small specimen, the dorsal valve having about four or five strong undulations upon the surface : the 
cardinal extremities are strongly deflected. 
4 b. Cardinal line, showing imperfectly the deltoid foramen. 
4 c. A small specimen, having about six distinct undulations on the disc, and three less distinct ones towards 
the beak : the shell bends abruptly upwards, nearly at right angles to the disc. 
4 d. A small shell, exhibiting very indistinct undulations upon the surface, being very abruptly deflected near 
the margin, and extremely extended on the cardinal line. 
4 e. A larger specimen, showing about four or five distinct undulations on the dorsal valve, and the same 
number on the ventral valve. The cardinal line is more extended than is usual in this species. 
4 f. Ventral valve and cardinal line of the same specimen, showing the narrow almost linear area; the latter 
enlarged, exhibiting the perforation in the beak. 
4 g. Lateral view of the same specimen, showing the abrupt deflection and elevation in front. 
