446 PALEONTOLOGY OF ILLINOIS. 



small basal pieces, surrounded by and alternating with somewhat 

 larger subradials, which in their turn alternate with and support five 

 larger, thick first radials, with articulating facets occupying their entire 

 breadth above, for the reception of the next range of radials. These 

 radials being in contact with each other all around, leave no spaces for 

 anal or interradial pieces. All the specimens then known had lost the 

 arms, but those of other species now before us are seen to be simple 

 from their origin on the second radial pieces, and each composed of a 

 single series of transversely oblong pieces. 



Subsequently another species was found in the same beds in Illinois, 

 presenting an obconic form of body, with a protuberant base, and we 

 were so much impressed with its resemblance to an East Indian Car- 

 boniferous type described by Dr. DE KONINCK, under the name Philo- 

 crinus, in 1863, that we were led to think our genus not distinct, and 

 his name having priority of date, we referred the two forms we had 

 first described to it.* In doing this, however, we thought it desirable 

 to change the specific name of our species typus, it not being the type of 

 the genus Philocrimis. 



We were led to regard our species as not being generically distinct 

 from Philocrimis^ because they agree exactly in all their known generic 

 characters, unless the lower range of pieces shown in the figure of Philo- 

 crinus really are the basal pieces, which would make that genus without 

 subradial pieces. As the typical specimen, however, seems from the 

 figure to be a little defective at the lower extremity, and the lowest 

 range of pieces represented, if really prolonged to the bottom of the 

 body, would have to present a very remarkably elongate cuneiform out- 

 line, we were strongly impressed with the probability of there being 

 another smaller series of true basal pieces below the lowest range rep- 

 resented (but not visible in consequence of the condition of the speci- 

 men), especially as these forms appear to agree so nearly in other 

 respects. If so, there would be no generic differences between PMlo- 

 crinus and Erisocrinus, and the American species would have to stand 

 under the former name. If Philocrimis, however, really has no sub- 

 radial pieces, then of course Erisocrinus must be an entirely distinct 

 genus. Until all doubts on this point, however, can be removed, we 

 finally concluded to retain our name Erisocrinm. 



* Our later comparisons of the other specimens have led to the conclusion that these are only varie- 

 ties of one species, (lood specimens of a form described by us in the Proceedings for August, 1865, 

 from a number of detached plates under the name B. tnbercidatns, also shows that it does not belong to 

 this genus, as it has a large, oblong subanal and a true anal piece resting on the upper truncated edge 

 of one of the subradials. Hence, although it agrees exactly i" all its other known parts with Enso- 

 erinus, it cannot properly be retained in that .genus, but would belong to Cyathocrim/*, giving that 

 group the limits generally admitted. It is not a typical Cyatlivcrinus, however, but nearer the group 

 Barycrinus, and yet differs from the typical forms of that group in having its second radials as wide as 

 the first, and articulating by broad, transversely furrowed facets, instead of merely resting in compara- 

 tively small sinuses in the upper edge of the latter. 



