88 



DAVKNI'ORr ACADKiMV OF NATURAL SCIKNCE.S. 



DESCRIPTIONS OF SOME NEW BLASTOIDS FROM 

 THE HAMILTON GROUP. 



BY W. H. HARRIS. 



Syn.- 



Ei,.4iACRiNLis Roemer.* 



Pentremites Troost, 1841, 6th Rep. Geol. Tennessee. 



Nucleocrinus Conrad, 1843, J""''- Acad. Nat. Sci. Phila., Vol. VIII., p. 280. 



Olivanites Troost, 1850, Cat. name. 



Elceacrinus Roemer, 185 1, Monog. Blastoidea, p. 55. 



Olivanites I^yon, 1857, Geol. Surv. Kent, Vol. III., p. 490. 



Nucleocrinus Lyon and Cass., 1859; Hall, 1862; Shumard, 1862. 



Ela;acrinus Shumard, 1866, Trans. St. L. Acad. Sci., p. 368. 



Nucleocrinus, canadensis? Montgomery, 1881, Can. Nat., Vol. X., No. 2. 



El^acrinu.s obovatus Karris, Nov. Sp. 



Plate I. — Ftff- i- ElsEiicrinus obovatus, hirg^e size, lateral view. 

 Fig. 2. Elteacrinus oliovatus, smaller size, anal side. 



Body obovate or elongate-balloon shaped, 

 more than once and a half as long as wide ; 

 upper half wider than the lower, semi-ovoid; 

 greatest width at about two-thirds from the 

 base; lower half gradually increasing in 

 width to the distal end of the ambulacra; 

 base truncate, with a deep concavity, which 

 is filled by the column. Cross-section pent- 

 angular, with straight or very slightly con- 

 vex sides, except along the basals, where 

 the sides are somewhat concave, and the 

 section more stellate. 



Pig. 3, cross-section of the hy- 

 drospires of Eheacrmtis ohovatiis 

 Barris. Enlarged two diameters. 



* At the sug-g-estion of Mr. Charles Wachsmuth, and in conformitv with the views of the late 

 Dr. Shumard (Cat. Palaeoz. Foss., in the Trans. St. L. Acad. Sci., 1866, p. 36S), I give Roe- 

 nier's later name, Ehearrhius, preference over Nucleocrinus Conrad. Conrad's entire descrip- 

 tion is as follows: " Ntich'ocrinus CQX\r\n\. The genus differs from Pejilremites Say, in hav- 

 ing only one perforation, which is central." In this description the only distinguishing charac- 

 teristic is erroneous, the accompanying figure poor and incorrect, and Hall's excellent descrip- 

 tions of Nucleocrinus were published ten years later than tho.se of Ela'acrinus. Roemer, in 

 proposing the latter name, gave a good definition of the genus. He found the central ajierture, 

 which Conrad had pronounced "the only perforation at the top," closed in perfect specimens, 

 and surrounding it he discovered one large and ten smaller openings. 



