Autodetas and Par amorphic Shells. — Clarke. 
333 
Fig. 12. Apertural 
view of Protocn- 
lyptroea marshalll. 
x:f. 
tions arc preserved the external spiral is oblique, composed of 
one and a half volutions, extends for about one fourth the 
height of the shell and thereupon becomes lost in the abrupt 
expansion of the next and last volution. The growth of the 
body whorl is very rapid, giving the shell when viewed from 
beneath precisely the same character as that possessed by the 
recent genus Calyptrona. 
In the species from the Stylioln limestone. 
though the apex is lost the form and sculp- 
ture are the same as that of the Naples species, 
and our specimen is broken in such a manner 
as to demonstrate the dextral coiling of the 
shell. 
These two dextral Devonian shells are clear- 
ly gastropodous ami their concurrence with 
species of similar exterior, but with a sinis- 
tral coiling, whose nature appears from all the evidence to be 
annelidan, is at least an interesting coincidence. The former 
are, however, of still further interest in representing a novel 
gastropod type for the Palaeo- 
zoic faunas, differing from Cli- 
siospira of the Ordovician in its 
normal coiling and minute spire, 
and which it is now proposed to 
designate by the name Protoca- 
hjl>l rn a . 
So far as I am aware, then' is 
but one other representative of 
this ancient calyptraeid "genus 
recorded from the Palaeozoic fau- 
nas, namely, the species de- 
serilie.l hxr Hi,. «• ri t ( .i- •■< ( •,, ,, ,,h, a ViR - 1:! Protocalyptrcea atyliophila. 
sMiheU 0} the wtltel as ( apulUS Htyliotalimestone.tanandaigualake, 
gateroides, from a corresponding ' " 
horizon (Intumescens fauna) al Rtlbeland in the Hartz moun- 
tains.* This is a shallower, less conical shell than the Amer- 
ican species, with a less conspicuous spiral and a pronounced 
oval marginal outline, but with similar surface sculpture and 
internal structure. The occurrence of all the known members 
*Fauna des [berger Kalkes; Neues Jahrb. fur MineraL, etc., lietl, Bnd 
::. 1884, \>. 303, pi. 5, M-. 12. 
