INVERTEBRATES. 319 



radial pieces, unknown. Height, to summit of first radials, 

 0.20 inch ; breadth of do., 0.34 inch. 



This species will be at once distinguished from young specimens of the last, 

 of its own size, by its obconic, instead of basin- shaped cup. From Professor 

 de Koninck's species cometa (in case our species should really belong to his ge- 

 nus), it will be distinguished specifically by the less convex outline of the sloping 

 under sides of its cup, as well as by its shorter and proportionally wider first 

 radial pieces. It will of course have to take the name Philocrinus conoideus, in 

 case Professor de Koninck's species should prove generically identical with 

 these American species. 



Locality and position : Springfield, Illinois; Upper Coal Measures. 



Erisocrinus tuberculatum, M. and W. 



Erisocrinus tuberculatus, Meek and Worthen, August, 1865. Proceed. Acad. Nat. Sci., 

 Philad., p. 150. 



Although we only know this fine species from its detached plates, these agree 

 60 exactly in form with the corresponding parts of our Erisocrinus typus from 

 the same beds, that scarcely a doubt can be entertained in regard to their be- 

 longing to the same genus, while they differ so remarkably in their surface 

 characters as to be distinguished at a glance, specifically, from that or any 

 other Crinoid known in our Coal Measures. This difference consists in their 

 entire external surface being covered with regularly disposed, narrow, promi- 

 nent tubercles, instead of being smooth. 



Of these tubercles there are, on a first radial plate measuring 0.90 inch in 

 breadth, and 0.54 inch in height, about thirty in number, arranged so as to 

 form two rows of about eight each, ranging parallel to the inferior sloping mar- 

 gins, and one row of about eight along the superior margin. Between this 

 latter row and those below, there are usually a few tubercles, either isolated or 

 forming a third transverse row. There is likewise usually one or several others 

 at the lower middle angle outside of the regular rows. This arrangement of 

 the tubercles into rows is not, however, always obvious at a first glance, but a 

 tendency to such a disposition can always be seen. 



On the second radials the tubercles are arranged in a single row along the 

 lower and each superior sloping margin, with one or more in the middle 

 between the rows. In the articulating or connecting surfaces of the radial 

 plates, we observe no differences between these pieces and those of the corre- 

 sponding parts of E. typus. 



Some of the plates indicate a transverse diameter of 1.40 inch for the entire 

 body. 



