25$ PROCEEDINGS OF TtlE ACADEMY Of 



pieces, and on the interradials much stronger lines parrallel to their inferior 

 sloping sides. 



Length, 0*G7 inch ; breadth, - 44 inch. 



At a first glance, this species might be mistaken for fhe common Pentremites 

 melo, of Owen and Shumard, from which it may be readily distinguished by 

 several well marked characters. In the first place it is narrower in proportion 

 to length, and differs in having its pseudo-amhulacral areas prominent instead 

 of sunken, and bounded on either side by a sharply elevated thin carina ; 

 while its interambulacral areas are flat, or even a little concave, towards the 

 lower part of the body, instead of being convex. It likewise differs in having 

 scarcely a visible line, instead of a deep furrow along the sutures between the 

 radial pieces ; while its b3se is much larger, and not sunken, but on a level 

 with the lower ends of the radial pieces, which are likewise more protuberant 

 at the lower ends of the pseudo-auibulaeral fields. 



In its larger and more prominent base, our species agrees more nearly with 

 a form described by us as a variety of P. melo, under the name P. melo, var. 

 projeclus, from which, however, it differs in all the other peculiarities men- 

 tioned. We now regard that form as a distinct species from P. melo. 



Compared with P. elongatus, of Sliumard, which it resembles in general 

 form, it will be at once distinguished by its greatly narrower and more promi- 

 nent pseudo-amhulacral areas,. larger radial pieces, and proportionally larger 

 interradials, which extend up to near the centre of the summit. These two 

 forms may be regarded as the connecting links between the true Pentremites 

 (P. Godoni group) and the /-'. melo, or Granatocrinus group. P. elongatus, 

 however, falls clearly into the former, while the form under consideration 

 belongs to the melo group. 



Named int honor of Dr. B. F. Shumard, of St. Louis, Missouri, who has 

 given more attention to the Blastoidea than any other person in this country. 



Locality and position. Burlington, Iowa, lower part of Burlington group 

 dI Suhcarboniferous series. Mr. Wachsinuth's collection. 



Gbanatockinus Norwoodi, 0. & S. ? 



Amongst some interesting Crinoids, loaned us for investigation by Mr. 

 Wachsmuth*, from the Burlington group at Burlington, Iowa, there is a 

 beautiful specimen, "resembling G. Norwoodi more than any other spe- 

 cies known to us, with all the numerous little jointed, thread like arms, 

 and a portion of the column attached. So far as we know, this is the only 

 specimen of this group ever found with the arms attached. As might have 

 been inferred from analogy, the arms in this type are apparently, in all re- 

 spects, exactly as in the true Pentremites. About thirty of them can be 

 counted arising from each pseudo-ambulacral area, though this is probably not 

 the entire number, as they are folded together so that many of them may be 

 hidden. They are very slender, simple, of uniform size, without any percep- 

 tible, taper, and composed each of a single row of pieces as long as wide, of 

 which about seven may be counted in the space of O10 inch. We are not 

 sure they are entire, though it is evident that those attached near the lower 

 pari of the areas must be at least twice as long as the body. The column 

 neaT the base is round and composed of thin pieces of equal size, but farther 

 down there are wider ones, with smaller between at regular intervals. 



The body of this specimen is partly hidden by the arms, but as far as can 

 be determined it is as stated above, much like G. Norwoodi, with the following 

 differences : In the first place, the parts of its radial pieces forming the inter- 

 ambulacral spaces are not more than halt as wide as in specimens of G. Norwoodi 

 of the same size. These surfaces also slope inwards laterally, so as to form 

 a rather deep groove along the suture between each two radial pieces, instead of 

 forming a flat area across between the pseudo-ambulacra, as in G. Norwoodi. 

 Again its pseudo-ambulacral areas are proportionally nearly twice as wide as in 

 G. Norwoodi, while the portions of the surface exposed are more coarsely granu- 

 lated than in that species, and the granules differently arranged. As it seems 



[July, 



