PLATE 84. 



Fig. 1. 369. 4. Cyrtolites oknatus. (P^g- 308.) 



1 a. Liitural view of a cast of this species. 1 h. Piufile of the yame, looking into tlie aperture. 



1 c. Another specimen (a cast), where the volutions are contiguous. 



1 rf. A specimen preserving the shell, from which the finer stria; are removed. 



1 e. A portion of the surface of the shell, showing the sculpture. \ f. Part of the same magnifieil. 



1 g. A transverse section of the shell. 



Fig. 2. 249. 1. Teocholites ammonius. (Pag- 309.) 



2 a. A small specimen, partially preserving the shell in some parts, and showing the sejjta in others. 



2 b. An enlarged portion of the surface, which is partially exfoliated, and slightly difierent from similar mag- 

 nifed parts of those in the Trenton limestone, where the shell is well preserved. 



2 c. Mould of a large specimen in the black slate. 



Fig. 3. 370. 2. Trocholites planorbiformis. (Pag- 310.) 



3 a. Figure of a specimen nearly entire. 3 ft. Dorsal view of the same. 



3 c. Ventral view of a fragment, preserving part of the two outer volutions, showing the concave ventral side, 



and the position of the siphuncle. 

 3 c*. Section of the outer volution. 3 d. A portion of the surface magnified. 



3 e. A specimen crushed in a vertical direction, a part of the outer volution retaining its form. 

 3/. Dorsal view of the same, showing the slightly arching septa upon the dorsal line, and a part of the outer 



chamber. 



