NATUEAL SCIENCES OF PHILADELPHIA. 137 



Descriptions of New Carboniferous FOSSILS from the Western States. 



BY F. B. MEEK AND A. H. WORTHEN, 



Of the Illinois State Geological Survey. 



ECHINODEEMATA. 



Genus POTERIOCRINITES, Miller. 



The typical forms of this genus have a more or less obconical body, with a 

 protuberant base, strong rounded column, and generally long, stout, bifur- 

 cating arms, always composed each of a single series of pieces. The body is 

 composed of five basal pieces, alternating with five subradials, and five first 

 radials, all alternating with the latter, excepting one on the anal side, which 

 rests directly upon the upper truncated edge of one of the subradials. 



The anal series consists, normally, of two alternating vertical ranges of 

 pieces, the lowest piece of which rests between the upper sloping sides of two 

 of the subradials, partly under one side of the first radial on the right, and 

 connects above its middle, on the left, with another resting on the upper 

 truncated edge of one of the subradials, and joining the first radial on the left, 

 while usually one or two more above these connect with others belonging 

 more properly to the b«se of the so-called proboscis. The primary radials 

 above the first are free, and generally smaller, and vary in number in the dif- 

 ferent rays of the same individual, from about two to eight, ten, twelve or 

 more, below the first bifurcation. The ventral part of the body is produced 

 upward in the form of a cylindrical, or more or less expanded proboscis (so 

 called), generally as wide as the whole space between the arms below, and 

 composed of regular hexagonal pieces, often with pores passing through the 

 sutures between. The opening is said to be near the top of the proboscis, 

 though we have never seen it in any of the numerous specimens we have ex- 

 amined. 



In addition to the species agreeing in all respects with the characters above 

 given, there are numerous others which, although conforming in general 

 structure with the typical forms, still depart so widely in some of their char- 

 acters, that when the extremes are compared, it seems difficult to believe that 

 they can all belong to one genus. And yet they are all linked together by so 

 many intermediate gradations that, in the present state of our knowledge of these 

 fossils, we are at a loss to see how they can be separated more than subgene- 

 rically. For some of these types the names Scaphiocrinus, Zeacrinus, Coeliocrinus, 

 etc., have been proposed, either as subgenera or as distinct genera from Pote- 

 riocriniles. Adopting the former view, these groups may, in order to facilitate 

 their study, be arranged as follows, commencing with Foteriocrinites proper: 

 1. — Genus Poteeiocriniteb, Miller. 



Represented by such forms as P. crassus, Miller, P. conicus, Phillips, P. Mis- 

 sourien.sis, Shumard, and P. Swallovi, M. and W". 

 2. — Subgenus Scaphiocrinus, Hall ; or Graphiocrinus, de Koninck and Le 



Hon.- 



The characters distinguishing this group, as it is generally understood, from 

 Poteriocrinites proper, may be stated as follows : Species generally of smaller 

 size and less robust habit, with only two (or rarely three) primary radial pieces 



* It seems highly probable, as has been suggested by Mr. Lyon and Dr. Shumard, that 

 the type on which de Koninck and Le Hon founded their name GrapMocrinm, may have 

 five minute basal pieces hidden by the column in the concavity of the under side, within 

 the range apparently belonging to the basal series, as is the case with many American 

 forms. If so, the typical form of &t/y»/tiVjcnj!i<s would present no difference of even sub- 

 generic importance, and the name Scaphiocrinus would have to be abandoned ; in which 

 case the American species would have to be called Graphiocrinus simplex, G. spinobrachia- 

 tus, G. trirtuosus, &c, 



1869.] 



