SYNOPSIS OF GENERA. 
lvii 
APPENDIX. 
Observations upon the genus Pernopecten, and allied genera.* 
PERNOPECTEN, Winchell. 
Proc. Acad. Nat. Sci. Philadelphia, p. 125. 1865. 
[Type Aviculopecten limiforinis, White and Whitfield.] 
In part Entolium, Meek. Geol. Snrv. California, vol. i, p. 479. 1865. 
“ Generic Characters.—Shell bivalve, sub-equivalve, monomyary. Valves 
more or less inequilateral and auriculate. Hinge-line straight; hinge furnished 
with a central, triangular cartilage-pit, and a transverse plate bearing on each 
side of the middle, a series of smaller pits, diminishing in size and depth from 
the centre outward. The shell seems to be thin, and probably has a structure 
more like Peden than PernaP 
Fig. 1. Pernopecten limiformis. A view of the type specimen of the species and of the genus 
Burlington sandstone. Burlington, lown. 
Fig. 2. An enlargement to two diameters of the cardinal portion of the preceding as obtained from a 
gutta-percha impression, showing more clearly the characters of the hinge. 
Fig. 3. Pernopecten Shumardanus. An enlargement of the cardinal portion of one of the type speci¬ 
mens of this species, showing the characters of the hinge. Waverly group. Newark, Ohio. 
* These observations were written in 1884 to accompany a general description and discussion of the 
Palaeozoic Monomyaria, and formed a part of the original plan for the introduction to the present volume. 
The discussions of the genera of the Monomyaria have been deferred for the present, but as the genus 
Pernopecten has been recognized in the Report of the State Geologist for 18S2, and also referred to in note, 
p. 81, Pal. N. Y., vol. v., pt. 1, Lamellibranchiata, 1, it is necessary to introduce here the portion treating 
of Pernopecten and allied forms. 
H 
