356 PROCEEDINGS OF THE ACADEMY OF 



])ieces are less prominent, so as to 'give its body a less spreading appearance. 

 Judging from the description, the B. laura, Hall, (sp.), would seem to be 

 somewhat like our species, but that form must be more depressed and pro- 

 portionally wider, and is also said to have the arm-openings directed upward, 

 which would even place it in a different section of the genus. 



We place this species provisionally in the Erelmocrinus group, from its gene- 

 ral appearance, as we have not seen any specimens showing the arms. 



Locality and position. Lower division, Burlington group, of Lower Carboni- 

 ferous, at Burlington, Iowa. No. 14 of Mr. Wachsmuth's collection. 



Genus PENTREMITES, Say. 

 Pentremites (Troostocrinus?) Woodmani, M. and W. 



Body attaining a large size, pyramidal-subovate,as seen in aside view, being 

 broad below, and produced and gradually narrowing upward ; strongly pent- 

 agonal as seen from above and below, in consequence of the projecting and 

 actually cariuated character of the radial pieces. Base strong, from two and 

 a half to three times as wide as high, trilobate in general outline below, and 

 very broadly and profoundly excavated along the three sutures, (the excava- 

 tions being continued out beyond the base into the lower ends of three of the 

 radial pieces) ; two of them pentagonal and tricarinate, and one quadrangular 

 and bicarinate, the carinte projecting considerably below the deeply sunken 

 facet for the attachment of the column, so that when placed erect on a level 

 surface the body stands upon these carinas, like a tripod upon its legs. Radial 

 pieces long and narrow, or about three times as long as wide, and gradually 

 tapering upward ; all extremely prominent along the middle and sloping strongly 

 inwards laterally, very sharply carinate below the pseudo-ambulacral areas. 

 Summit openings very small and closely approximated. Interradials very 

 small, or only about one-tenth as long as the radials. Pseudo-ambulacral 

 areas remarkably narrow or sublinear, and deeply sunken, extending down 

 rather more than half the entire length of the body, or about two-thirds the 

 length of the radial pieces; pore pieces minute, slightly oblique, and number- 

 ing about 100 to each side of each area, the two rows of each area being sepa- 

 rated by a deep mesial furrow, along which the inner ends of the pore pieces 

 are minutely crenale, lanceolate and supplementary pore-pieces unknown. 

 Surface marked with microscopic lines, as fine, regular, and crowded, as if 

 made by an engraver's ruling machine. 



Height, 2-25 inches; breadth, 1 64 inches. Breadth of base, 1-14 inches; 

 height of do., 050 inch ; depth of excavations along the sutures of base, 0-20 

 inch ; breadth of do. from 0-45 to 0-56 inch. Length of pseudo-ambulacral 

 areas, 1-45 inch ; breadth of do., 0-08 inch. 



This extraordinary form differs so widely from all other known species, as 

 to render a comparison of its specific characters with any of those hitherto 

 described entirely unnecessary. It seems to be related to a group of species 

 characterized by a triangular base, and very narrow pseudo-ambulacral areas, 

 for which Dr. Shumard has proposed the name Troostocrinus. Still it presents 

 some rather strongly marked differences from that group, the species of which 

 have the body narrow, fusiform, and more or less elongate and tapering below, 

 with the triangular base merely flattened on each of the three sides. In our 

 type however, the body is broadest below, while the base is comparatively very 

 short and wide, and has the three spaces corresponding to the flattened sides 

 of the typical species of Troostocrinus so very profoundly and broadly exca- 

 vated, as to impart a very remarkable appearance to the lower part of the fossil. 

 Should it be thought desirable to designate this type by a distinct subgeneric 

 name, it might be called Tricodocrinus, in allusion to the three deep excava- 

 tions of the base. 



The specific name of this form is given in honor of Mr. 11. T. Woodman, of 

 Dubuque, Iowa, to whom we are indebted for the use of the only specimen 

 we have seen. 



Locality and position. — Salem, Indiana, Lower Carboniferous, Keokuk Group ? 



[Dec. 



