1885.] NATURAL SCIENCES OF PHILADELPHIA. 243 



the basals, radials <>r forked pieces, and the deltoid pieces or 

 orals." 1 



The latter statement seems to us an anomaly. It is impossible 

 that those plates can be orals, and at the same time form part of 

 the calyx. The orals in recent Crinoids have never been con- 

 sidered as calyx pieces, and hence, if the deltoids are orals, they 

 do not belong to the calyx. That, however, they are calyx 

 plates is indicated by their position and relations to other parts, 

 and still more by their enormous variation in size among species 

 of the same genus. If the deltoids were orals, the actinal 

 system in the Blastoids, in forms like Elseacrinus obovafus. 

 would occupy over three-fourths of the entire test, while in 

 Heteroschisma,Y?hich has exceedingly small deltoids, these regions 

 would be reduced to a small circum-oral space. The proportions 

 of the actinal and abactinal regions in the test, respectively, 

 were looked upon by Prof. L. Agassiz as determining the 

 different outlines of the various " orders " of Echinoderms, 

 which he ranked according to the greater preponderance of the 

 one over the other, and this, if true, proves conclusively that the 

 deltoids are not actinal plates, and, therefore, are not orals, but 

 must be interradials. The same argument, however, cannot be 

 applied to the Cyathocrinidae. in which the so-called orals are 

 located ventrally. and from analogy with recent Crinoids should 

 be actinal plates. 



By carefully removing the arms in some of our best specimens 

 of Gyathocrinus, we succeeded in exposing the ventral surface in 

 several species, and were enabled to observe its structure in 

 various stages of preservation. In a specimen of Gyatkocrinus 

 Gilesi (PI. 4, fig. 2), from the Burlington and Keokuk Transition 

 beds, we found in situ the five large interradial plates, the so- 

 called orals, all connected laterally, and each one provided along 

 its upper face with a conspicuous central node. In another 

 specimen of the same species (PI. 4, fig. 3), these interradials 

 were partly covered along their surface by numerous irregular 

 pieces, but so as to leave the central node exposed, the face at a 

 level with the small tegminal pieces. In two specimens of 



1 We are pleased to state that Dr. P. H. Carpenter, whom we had 

 acquainted with the modification of our views regarding these plates, now 

 fully agrees with us that neither those of the Blastoidea nor Cyathocrinidaa 

 are orals (see C'hall. Rep., p. 162). 



