MELOCRINID^. 269 



the arms. The arrangement of the larger plates at the summit is also irreg- 

 ular, being unlike that of orals, which probably are not represented. Anal 

 opening excentric, at the summit of a small protuberance. Column round ; 

 axial canal large, pentalobate, the lobes directed interradiallj, except in one 

 species in which the stem is pentangular and the central canal radially 

 disposed. 



Bistrihidion. — Glyptocrinus^ as now amended, is confined to the Trenton 

 and Hudson River groups, and probably is restricted to America. 



Ti/pe of the genus. — Glypiocrinus decadadylus. 



Remarks. — The genus agrees in the uniserial arms and its general 

 structure with Mariacrinus, but that has four basals instead of fi\Q, It 

 resembles Compsocrinns, which has also four basals, but an anal plate in 

 line with the radials, which throws it into the Batocrinidse. 



The European species referred to Glyptocrinus, with the possible excep- 

 tion of G. hasilis, belong to other genera. The specimens described under 

 the name Glyptocrinus glohularis by Nicholson and Etheridge probably belong 

 to Archceocrinus. They evidently had infrabasals, for the interradials rest 

 upon the basals, and they probably had biserial arms. 



The following species either are synonyms, undeterminable, or are 

 removed from Glyptocrimis to other genera : 



Olyptocrinus parvus Hall, referred to PtycJiocrinus. 



" angularis Miller and Dyer, synonym of . . . . Ptyahocri7iiis parvus. 



" gracilis Wetherby, synonym of Ftycliocrinus parvus. 



" Harrisi Miller, referred to Compsocrinus. 



" (7ar%^HALL, " Mariacrinus. 



'' miamiensis Miller, " Compsocri?ius. 



Baeri Meek, " Xenocrinus. 



" ea^i?a/isws Phillips, " Sagenocrinus. 



'' armo5z^5 McChesney, " Siphonocrinus. 



" siphonatus Haja., Bynowjm oi Siphonocrinus armosus. 



" nobilis Hall, referred to Siphonocrinus. 



" cognatus Miller, synomym of . Reteocrinus Onealli. 



" O'Nealli (Nealli) Hall, " Reteocrinus. 



" Zacimosws Billings, '^ Archwocrinus. 



" suhnodosus Walcott, " Rhaphanocrinus, 



" sculptus Miller, " Rhaphanocrinus. 



" argutusY^K^QOTT, " Stelidiocrinus. 



" i?H5m5 Billings, ^^ ........ Periglyptocrinus. 



^' fimhriatus Shumard, undeterminable. 



" libanus Safford, not defined. 



'' plumosus Hall, detached column and arms. 



" quinquepartitus Billings, detached column and arms. 



" PattersoniMiiji.TL-R, undeterminable. 



