916 Report oF THE STATE GEOLOGIST. 
they may all be safely included under the old family designation 
introduced by Kurorea in 1848, SrpzoNnorRETIDE. 
Crania and its allies (CRanmiia, Psrupoorania, PHoxtpops) 
constitute a group in which, thus far, there is no satisfactory evi- 
dence of the existence of the pedicle, and we are left to the assump- 
tion that this organ became atrophied at a very early growth-stage. 
The study of recent Cranias has not yet determined this point, but 
will probably ultimately accomplish thisend. At whatever stage 
of growth the pedicle was lost, we may infer that its disappear- 
ance was directly followed, in Cranza, and generally in Ora- 
NIELLA, by a solid fixation of the animal by the substance of one 
of the valves. In Puoxipors there was no such cementation, but 
at a correspondingly early stage the shell became wholly inde- 
pendent. All these shells with central or subcentral beaks have 
an external resemblance to Orxicutorpra; the formation of the 
secondary growth of the valves behind the apices or position of 
the protoconch, is a further substantial agreement with the Dra- 
OAULIA as contrasted with the abbreviated posterior peripheral 
shell-growth in the Masocautra (Lineuta, Oxsoxvs). It is never- 
theless to be observed that no trace is found on mature or imma- 
ture shells, of a former pedicle-slit, incision or perforation, and it 
would be difficult to comprehend in what manner such an essen- 
tial modification of the shell could be wholly concealed by later 
growth.* Were the pedicle marginal in primitive growth-stages, 
and subsequently atrophied, the obliteration of the marginal 
opening by later resorption and growth would be a readily intel- 
ligible process. There is, hence, in this default of evidence, a 
good reason to doubt the close affinities of Cranra and Pxoripors 
to the Dracaur1a. Present knowledge would seem to indicate 
that they were primarily of the type of the Mxsocaurta, and that 
their resemblance to the Dracauria is wholly of secondary 
growth.t Waacen’s term for this group GasreropremaTa (or 
CraniackA), may therefore prove to be equivalent to each of 
these other two divisions. 
* Quite early conditions of Crania siluriana and Craniella Hamiltonie, from 1.5 to .6 mm. 
in diameter, are fully cemented. Examples of Pholidops Hamiltonie, not above .6 mm, in 
diameter, give no indication of a pedicle-passage or surface characters not present in the adult. 
+Some species of PHo.tipors (P. arenaria, P. linguloides) have a terminal submarginal 
apéx; and their resemblance exteriorly to the oboloids is very striking This is, however, no 
more than a resemblance, as they show, on the under side, the same mode of peripheral 
growth beneath the beak as the other forms of the genus in which the umbones are more 
nearly central. 
168 
