1887.] NATURAL SCIENCES OF PHILADELPHIA. 99 



"proboscis" plates as representing the orals, and, so far as Ave know, 

 they never afterwards, until the appearance of the Blastoid Catalogue, 

 gave any other interpretation of the inner ring of plates. If they 

 had regarded them as orals, it would have suggested the j)resence 

 of two rings of orals, the one within the other. 



Subsequently we found reason to distinguish two rings above the 

 radials the so-called orals or deltoids of Etheridge and Carpenter 

 and a series of summit plates the so-called "proboscis" from a 

 specimen of S. gemmifonms; and we communicated this fact to Dr. 

 Carpenter as early as Dec. 17th 1885 with a diagram explaining it, 

 stating that, although summit j)lates in our specimen were not 

 preserved, such plates were probably represented in the species. We 

 also informed him that it was the third ring or deltoids, and not the 

 summit plates, which we took to be the homologues of the interra- 

 dials in Haplocrinus ; and that the hypothetical plates closing the 

 summit we took to be represented in Haplocrinus by the central 

 plate. At the same time Ave applied to Prof Whitfield for specimens 

 to ascertain the summit structure in S. angulatus. From these 

 specimens we at once found beyond all doubt that the plates of the 

 third row in S. angulatus, as well as in S. gemmiformis, do not extend 

 to. the oral center, but are followed by five other plates the so- 

 called "proboscis" covering the mouth (fig. 3). Upon making 

 this discovery Ave promptly declared the latter to be the orals, and 

 advised Dr. Carpenter accordingly on January 9th 1886. * 



Our statement, therefore, that the "ventral pyramid" in Stephanocri- 

 nus is composed of interradials, AA'as made with reference to plates Avhich 

 Ave then supposed to be a single element, extending to, but not 

 covering the oral center, and which Etheridge and Carpenter had 

 previously announced to be orals folloAved by vault pieces, but now 

 consider to be deltoids followed by orals. When the authors assert 

 that Ave applied the name "calyx interradials" to the "j^lates Avhich 

 form the ventral pyramid and cover the mouth of Stephanocrimis and 

 also of Hapdocrinus," Ave cannot help thinking that they are "going 

 very much too fiir." A similar erroneous statement Avas made by 

 Dr. Carpenter in March 1886 ^ and it has been a matter of consid- 



*It is due to Dr. Carpenter to state here tliat he had privately communicated to 

 us, after Sect. I of Pt. Ill of our Revision was in print, that he regarded the inner 

 ring of Stephanocrinits as orals, and this led to our correspondence upon the 

 subiect. 



lAnn. and Mag. Nat. Hist., March, 1886, p. 282 



