920 Report oF THE State GEOLOGIST. 
condition, it is not possible to give it great weight in a broader 
grouping of the genera, for we find that SiropHoneLia is 
but a reversed SrropHEoponta, passing through similar phases; 
Ampuistroputa is a reversed Braonyprion, both existing in faunas 
of the same age, and SrrorpHomENaA is a reversed RaFrInEsQuina, 
both similarly coexistent. 
With this presentation of the subject it seems neither necessary 
nor desirable to propose any broad division of this group of 
genera. In 1846 Kine proposed to embrace Str PHomeENa and its 
allies in the family Srropyomenip.». The large number of generic 
values allied to SrropHomEna, which have been determined since 
that date, make this comprehensive family divisible ad libitum, 
sed non in majorem Dei gloriam. 
The calcareous fixation of the pedicle-valve to extraneous 
bodies after the closure of the pedicle-passage and atrophy of the 
pedicle itself, is repeatedly manifested by these shells. This, as 
already shown, is a pre-adult condition in Orrnorsures, Derpya 
and Strertoruyncuvs, the shell becoming wholly free before full 
growth was attained; but in Lepranisca and Davinson1a the 
attachment was maintained throughout the later existence of the 
shell. 
The impressions left by the spiral arms upon the interior of the 
valves in Davisonia and Lepraxnisca, and also observed by 
Davinson in a specimen of Lafinesquina Jukesi, show a complete 
correspondence in the direction and curvature of the coils, and 
we are left to infer that other members of the SrropHomenID# 
were in agreement with this structure, and hence that the arms 
in their uncalcified condition approached nearer the calcified 
spirals of KowrvcKivip% (Ca@xosprra, Kontnoxrnia, etc.) than to 
those of any other group. 
The condition of the pedicle-passage possessed by these shells 
is maintained by Cuonerrs and Propucrus, without great modifi- 
cation in other respects. Congres possesses a marginal row of 
strong cardinal spines or tubes communicating with the internal 
cavity of the valves. Yet we are acquainted with forms (¢. ¢., 
Anoplia nucleata) in which these spine-tubes do not manifest 
themselves externally. Psropucrus is normally covered with 
spines on one or both valves, but there are some species which 
possess none. The cardinal area, deltidium and teeth, which are 
172 
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