1888. ] 4 231 . [Keyes. 
den. On the morning of the 22d of May he fell dead in the street from 
heart disease or apoplexy, it is not known which. 
We have lost in him a member who, perhaps, more than any one of 
us, deserved to be an associate in a Philosophical society, and one whose 
philosophy, however different from that popular in this community, 
prompted him all his life to be an affectionate son and brother, a warm 
and sympathetic friend, and a man of honorable instincts. 
On the Attachment of Platyceras to Paleocrinoids, and its Effects in Modify- 
ing the Form of the Shell. 
By Charles R. Keyes. 
(Read before the American Philosophical Society, October 19, 1888.) 
Attention has lately been called to the sedentary habits of Platyceras,* 
and to the variable configuration of the apertural margin in different indi- 
viduals of the same species—the confirmatory evidence being partly from 
analogy among living forms closely allied to the fossil ; partly, and more 
directly, by the actual occurrence of various Platycerata attached to palee- 
ozoic crinoids. The association of these gasteropods with the crinoids had 
long been known, but prior to the recent discovery of a rich crinoidal 
fauna in the Keokuk rocks of Indiana illustrative examples of this kind 
were numerically very limited. The recorded instances of such findings 
have usually been accompanied by more or less brief explanatory remarks, 
but until 1868+ the interpretations were for the most part incorrect, chiefly 
on account of erroneous conceptions relative to the functions of various 
organs in the crinoid. It was, however, noted that the molluscan shells 
were nearly always on the ventral side of the crinoid in the proximity of 
the vault opening and encompassed by the arms—a fact which was 
thought to afford conclusive proof of the carnivorous habits of the crin- 
oids, which were, at the moment of perishing, in the act of devouring the 
mollusks. The examination of several fossil crinoids having shellfish in- 
closed by thearms led the Austins} to some general conclusions relative to 
the food of all the crinoids; and they give a vivid though highly imaginary 
account of the capture of Producti and univalves by the ‘‘rapacious”’ 
echinoderm. Another explanation of this phenomenon was subsequently 
advanced to the effect that the gasteropods were parasitic in their habits, 
but this also now appears to require considerable emendation. Later in- 
vestigations among recent and fossil crinoideans show that the food of the 
species now extant consists in great part of animalcules and microscopic 
* Keyes, Am. Jour. Sci., Vol. xxxvi, p. 269, 1888. 
+Meek.and Worthen, Proc. Acad. Nat. Sci. Phila., 1868, p, 310. 
t Monog. Recent and Fossil Crinoidea, p. 73, 1843, 
PROC. AMER. PHILOS. SOC. xxv. 128. 2p. PRINTED NOV. 24, 1888. 
