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PALAEONTOLOGY OF NEW-YORK. 
(*ENUS CrYPTONEHA (Hall, 1861). 
Ceyptonella : Hale, Fourteenth Report on the State Cabinet, p. 102. 1861. 
“ Id. Fifteenth “ •< «< pp. 132 & 133. 1862'. 
“ « Sixteenth “ <« <« p. 43. 1863. 
Shells equilateral, inequivalve, elongate, oval or ovoid ; valves unequally 
convex, without median fold or sinus, or with this character moderately 
developed and principally towards the base of the shell. Ventral valve 
with beak extended or incurved, perforate; foramen terminal, the 
lower side formed by two - small triangular deltidial pieces, or, in their 
absence, by the umbo of the opposite valve. Shell-structure finely 
punctate. Surface smooth, or with concentric striae. Valves articula¬ 
ting by teeth and sockets, the dental lamellae of the' ventral valve 
extending downwards into the cavity of the shell. The muscular 
impressions in the dorsal valve are strongly marked above, and extend 
in two narrow separated impressions more than halfway to the front 
of the shell : the ventral cast shows elongated muscular and vascular 
impressions. 
The species of this genus are more elongate than Merista and Meri- 
stella, and those now known are less distinctly marked by mesial fold 
and sinus; while the beak is more attenuate, often a little flattened, and 
rarely so closely incurved, as in the genera cited. The punctate structure 
of the shell is a distinguishing character. 
This genus was first described as above cited, and figures of the exte¬ 
rior form and of the interior of the valves were given in the Fifteenth 
Report. The results of some farther investigations were given in the 
Sixteenth Report, and an illustration of what was supposed to be the 
internal appendages of the shell. About the same time it was discovered 
that some punctate shells of the same general form possessed the loop of 
Terebratula proper; and it became a matter of great interest, and still 
greater difficulty, to determine the internal structure of the species. I 
had referred to this genus the Terebratula lens, T. lincklmni, T. reciirostra 
