1890.] NATURAL SCIENCES OF PHILADELPHIA. 155 



to be no serious objections to this inference. But with the uni- 

 valves their position throuy-h life indicates that their sustenance was, 

 in great part at least, of a somewhat different character. 



The anatomy of the crinoid and the position of the molluscan 

 shell are not in accord with the supposition that the calyptnean may 

 in anv way have been nourished on the food of the crinoid. This 

 woiiUl im[)ly that the gasteropod was parasitic in its habits, a view 

 wliich, though held by most writers, does not appear to be structur- 

 ally substantiated. While no doubt the Capulus derived the greater 

 part of its food from excrementitious matter, nourishment from other 

 sources may also have been obtained and in all probability it was 

 very similar to that of the crinoids and the living Calyptrajida^. 

 Furthermore there does not seem to be the slightest indication that 

 the crinoid was in any manner inconvenienced by the attachment 

 of the gasteropod, except, perhaps, in a few cases where the mollus- 

 can shell had encircled the posterio-lateral arms, Avhich were in 

 consequence slightly pressed outward. The only really noticeable 

 effect of the presence of Capulus on the crinoid is a comparatively 

 shallow depression or groove on some of the vault plates — marking 

 the position of the shell lip ; though in the majority of specimens 

 even this feature is not well pronounced (Plate II, figs. 6 and 7). 

 There are no grounds for the view advanced by TrautschohP in re- 

 gard to Cromyocrinus st«ip^e.i'Trauts. and its adhering Capttlus para- 

 siticus Tvsxnts. from the loAver Carbonic of Russia. He says: " Es 

 ist nicht unmoglich, dass der oben beschriebene cylindrische Pro- 

 cessus der Analplatten zum Schutz gegeu diese Verfolger des (V. 

 simj)lex aufgebaut ist." The " cylindrical jDrocess" here referred to is 

 manifestly a ventral sac and therefore was not caused by the pres- 

 ence of the gasteropod. 



Illustrative Examples. In some crinoids, as Gilbertsocrinus, the 

 plates of the vault are more or less convex or nodose. This nodosity 

 of the ventral plates reaches a high development in such forms as 

 G. tuberosue Lyon and Casseday, from Crawfordsville, Indiana. 

 Nearly one-half of the known individuals of this species have a 

 gasteropod adhering. The specimens illustrate well the adaptation 

 of the apertural margin of the shell to the irregularities of the 

 crinoid al surface, for it is clearly observable, as first pointed out by 

 ]\Ieek and Worthen, that the contact of the gasteropod shell and 

 crinoid is not the result of accidental pressure, but that the moUusk 



1 Die Kalkbriiche von Mjatsclikowa, p. IIS. 



