1887.] NATURAL SCIENCES OF PHILADELPHIA. 95 



compound deltoid and against the intermediate large anal plate, 

 and in all of them the loMer margin is perforated and occupied by- 

 one half of the anal aperture, thus showing that in this species also 

 the summit consists primitively of eight pieces, of which the suture 

 lines became partially obliterated. 



In the type specimen of Elaeacrinus melonijormis, which Dr. 

 Barris was kind enough to send us also, the arrangement of the 

 summit plates is the same as in E. ohovatm, and Ave clearly distin- 

 guished the small anal jjlate. 



It thus appears that in the known species of Elaeacrinns the 

 summit plates consist of a central plate surrounded by six or more 

 proximals, and that in no case do they consist of five primitive 

 plates ; so that the "simplest form of summit" five plates only 

 has not been found in Elaeacrinus. The assumed parallelism of 

 difiei'ences between E. elegans and E. Verneuili among tl\e Blastoids, 

 and Gidicoeriuus and the simplest form of Platycrimis among the 

 Crinoids, encounters a very serious interruption in consequence 

 unless, indeed, it should turn out that there is a parallelism in these 

 cases of an altogether different character from that contemplated by 

 the English authors. 



The summit of Orophocrimis stelUformis was stated by White ^ to 

 consist of "five small plates arranged like a five-pointed star, with 

 the points touching each of the upper ends of the interradial plates." 

 We do not doubt that Dr. White thought to observe such arrange- 

 ment, but Ave think it very probable that the condition of his sjDeci- 

 men was such that he overlooked the central plate, Avhich may 

 easily happen, as the sutures are often difiicult to observe. In a 

 large number of specimen? Ave have never found a single one with 

 the sunmiit com2:)osed of five jjlates only, or Avith a central plate 

 surrounded by five jDroximals. We found, however, that in speci- 

 mens of this species, as Avell in Granatocrinus Nonvoodi and Schizo- 

 hlastKS Sayi, Avhen the coA^ering plates are in place, they often partly 

 overlap the summit plates, and in such cases the arrangement of the 

 latter cannot be distinctly observed. When the coA^ering pieces are ab- 

 sent, and the summit plates alone are intact, as in several of our speci- 

 mens, the arrangement is quite regular. We have made a careful ex- 

 amination of a large series of specimens, not only of 0. stelUformis but 

 also of our new species 0. fusiformis and 0. conicus, in Avhich the sum- 

 mit plates are more frequently preserved. In all of them there is a 



1 Boston Journ. Nat. Hist. 1863, Vol. VIII, No. 4, p. 4S7. 



