ORGANIC DEPENDENCE AND DISEASE 
69 
case of such attachment to determine its casual or its in- 
tentional nature. It is in the Devonian that the growing 
abundance of the crinoids amid legions of Capulus begins 
to provide us with increasing instances of fixation of the 
latter to the former. The earliest of 
all these and the most striking case on 
record at all, is the combination of the 
crinoid Melocrinus micmac Clarke with 
the capulid snail Orthonychia tortuosa 
Hall from the fauna of the Lower Devo- 
nian Grande Greve limestone of Gaspe. 
Here we have a small species of Melo- 
crinus overwhelmed and borne down 
by a massive trumpet-shaped limpet, 
whose very weight must have toppled 
the crinoid over to the sea bottom. The 
aperture of the shell fits down over the 
entire dome of the crinoid naturally 
covering the eccentric aboral aperture. 
The attachment of the shell must have 
begun very early and continued firmly 
to the full maturity of the shell. Or- 
thonychia is a division of almost conical 
or slightly twisted capulids, the spire 
being apical and incipient or altogether 
absent. Such shells have not before 
been seen in this attached condition; 
they were not adapted to it, for their uncoiled form would 
make the crinoid so top-heavy that the whole combination 
would succumb. It is therefore not surprising that this 
record does not repeat itself . 1 
Craterocrinus ruedemanni Goldring is a species as yet 
i This specimen of M. micmac is the only crinoid ever found in the profuse 
Grande Greve fauna. It was obtained by the writer from a ledge a half fathom 
under water at low tide. 
Fig. 55. Melocrinus mic- 
mac, a Lower Devonian 
crinoid, embraced and 
almost overwhelmed 
by a trumpet-shaped 
snail. 
