PLATE 31 A. 

 Fig. 1. 141. 4. Lept^na alteenata. (Pag. 102.) 



1 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 J. A lateral view of the same specimen, sliowing 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 Conr.\d. 



In both the preceding specimens the beak is perforated, as is exhibited in the enlarged view of the 

 hinge in 1 o, which at the same time shows the foramen not quite closed. 



Tlie 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 t d 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 ii, 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 striae less distinct. 



Fio-. 2. 142. 5. Lept^na cabierata. (Pag. 106.) 



2 a. Lateral view of tlie 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-striate, from being denuded of the shell. 



Fig. 3. 143. 6. Lept^na deltoidea. (Pag- 106.) 



3 a. A specimen showing Ijut a slight difference from the last described species. It is marked by distinct con- 



centiic wrinkles U]ion 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 partalces of the characters of specimen 1 i. 



3 b. A specimen presenting the same form as the last, except tliat 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 tlie cardinal line, producing small acute ears. 



;i c. Lateral view, showing the elevation of the shell. 



3 d. A specimen of neai-ly the same form as the last. The concentric wrinkles are more distinct, and the ra- 

 diating striae 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 striie ; scai'cely 



produced in front. The strife on the centre are more distinct than at the sides. 

 3f. A very perfect specimen in form and markings, from a drawing by Mr. Conr.\d. 



Fig. 4. 144. 7. Lept^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 oh 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, sliowing 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. 

 if. Ventral valve and cardinal line of the same specimen, showing the narrow almost linear area ; the latter 



enlarged, exhibiting the perforation in the beak. 

 1 g. Lateral view of the same specimen, showing the abrupt deflection and elevation in front. 



