CRYPTONELLA OE THE HAMILTON GROUP. 
S© 7 
Cryptonella ? lincklseni. 
PLATE LX. 
Terebratula lincklceni Hall, Thirteenth Report on the State Cabinet, p. 88. 1860. 
«< << Idem, referred to Cryptonella ; Fourteenth Report on the State Cabinet, 
p.101. 1861. 
Cryptonella lincklceni : Idem, Sixteenth Report on the State Cabinet, p. 44. 1863. 
Shell ovate or subelliptical, usually broader below the middle, varying 
from moderately convex to very gibbous and sometimes subcylindri- 
cal; front rounded, subtruncate, or a little depressed. 
Ventral valve varying from moderately convex to gibbous, somewhat 
regularly arcuate in longitudinal outline, sometimes a little flattened 
towards the front or marked by a narrow mesial depression. Beak 
more or less abruptly incurved, and truncate by a foramen of mode¬ 
rate size : umbonal slopes rounded or subangular, and concave towards 
the cardinal margin. 
Dorsal valve varying from moderately convex to gibbous; the greatest 
convexity about the middle of the length, and thence curving regu¬ 
larly to the sides and base. 
Surface marked by fine concentric striae of growth, which are some¬ 
times crowded together towards the front, causing a thickening of the 
shell. Shell-structure distinctly punctate. 
The internal structure has not been determined, and I therefore refer 
it with doubt to the Genus Cryptonella. 
This species presents some variety of form, from subelliptical to 
broad-ovate. The length of a large individual is a little more than three- 
fourths of an inch, with a width of five-eighths of an inch and a depth 
of three-eighths;. while another form, which I refer to the same, has a 
length and width of half an inch, with a depth of a little more than 
a quarter of an inch. Some of the smaller individuals are a little more 
than a quarter of an inch in length. 
This species is common in certain beds; and for the most part is readily recog. 
nized. In the less gibbous speeimens, it resembles the O. jplamrostra,■ but the beak 
is more incurved, and , there is less angularity of the umbonal slope, while the 
outline is more regularly rounded. In a crushed and distorted condition, it is not 
readily distinguished from C. rectirostra. 
