Hambach — Revision of the Blastoideae. 39 



21. Pentremites suLCATUS,Eoemer,1852. Chester limestone. 

 Pentremites cherokeeus, Troost M. S. 



Pentremites robustus, Lyon. 



Pentremites laterniformis, Owf n and Shumard. 



The latter, which has been regarded as a synonym 

 for Pentremites obliquatus, is the cast of Pentremites 

 sulcatiis. The confounding of this species with 

 P. obliquatus must have been caused by assuming 

 that a cast of ohliquatiis would furnish an elongated 

 prismatic lower calyx part, as we have in P. laterni- 

 formis, which is due to the internally straight base 

 portion of the fork pieces in Pentremites suIcatiis, as 

 I have described and figured years ago. Moreover all 

 Pentremites laterniformis have been described as com- 

 ing from the Chester limestone, where such casts are 

 frequently met with, but the Saccohlastus obliquatus 

 (= P. laterniformis, Troostocrinus laterniformis, 

 Tricoelocrinus obliquatus) does not occur in this 

 formation and so far has been found only in the 

 Warsaw or Keokuk formation. 



22. Pentremites bradleyi. Meek. Subcarboniferous. 



2. Genus Cribroblastus. 



General form of body elliptical or globose, of medium size, 

 seldom over J inch vertical diameter. Ambulacrum narrow, 

 linear, and extending almost over the whole body. Central 

 opening never closed, except by ambulacral integument, sur- 

 rounded by eleven openings constructed by the junction of 

 deltoid and lancet piece, very small and never confluent with 

 each other. Anal opening on the posterior side between two 

 genital openings, from which it is separated by two fine septa. 

 Deltoid pieces 'very variable, occupying from ^V to f of the 

 interambulacral space. Base portion small, more or less 

 depressed. Column round. This genus will include the fol- 

 lowing species. 



