14 J. Hall on Cryptonella, Cenironella, Meristella, 
towards the beak. This character pertains to the limestone spe- 
cimens, while those in the Hamilton shales, as figs. 7 and 8, have 
thinner shells, and Jess deep and strong muscular i impressions. 
Ihave already (Thirteenth Report on the State Cabinet, pp. 73-75, 
and illustrations on p. 98) pointed out the distinction between 
Athyris= Spirigera and Meristella. This difference is everywhere 
clear and unmistakable, in the external lamellose surface of a 
= = the almost smooth character of the other. The mu 
impressions of the ventral valve of Athyris are at eh 
distinguishable from those of Meristella; as may seen on 
somparison of figs. 35 ae 36 with figs. 29 and 30. 
Fig. 35. Interior of ventral valve of Athyris spiriferoides.— Fig. 36, Cast of same. 
In the dorsal valve, the muscular impressions differ from 
parties a hinge plate is of somewhat different character, 
and the median ney is « is soarcdy developed, 
Note on the Ge —Among the specimens sent 
to me by Dr. Rominger, are ae individuals of Lepioceelia concava, 
showing the existence of internal spires; and a careful exam- 
ination of my own ieee from e Lower Helderberg group 
has shown several spec S possessing these internal organs 
which have their Bis a raced obliged outwards, ang are 
sion at the rocess, and below this is a flat ca a. 
_ A critical re-examination of the fossils seleered iocthis genus 
nal form and features, which, in the absence of Scored 
cigs tee legen 2 structure, were grouped together. A fr | 
i 
that there are at least three distinct types, in their exter, : 
2 
d 
3 
