338 PROCEEDINGS OF THE ACADEMY OF 



into the body with the end of the column in the specimen studied). Subra- 

 dials of moderate size, those seen hexagonal. First radials somewhat larger 

 than the subradials, a little wider than long, with a general subpentagonal 

 form; facet for the reception of the second radials about one-third as wide as 

 the upper side of the plate and excavated about one-third of the way down. 

 Second radial pieces very small, wider than long, and with the succeeding ra- 

 dials curving outward. Third radial in one of the rays nearly as long as wide, 

 expanded above and contracted below, and in this ray surmounted by a fourth, 

 which, like the third in each of the only two other rays seen, is a triangular 

 axillary piece, on which the arms rest, the upper angle being acute and so pro- 

 duced as entirely to separate the arm-bases, while the lateral slopes, on which 

 the arms rest, are distinctly concave. Anal piece unknown. 



Arms distinctly divergent at their origin on the last radials, as well as at 

 their succeeding bifurcations, dividing on the third piece in two of the rays 

 seen, and on the fourth in another, the pieces being rounded, nearly as wide as 

 long, somewhat constricted in the middle and a little dilated at their upper 

 ends, while all of the axillary pieces at the various bifurcations have much the 

 same form as the last free radials. Beyond the first bifurcations mentioned, 

 above the last free radials, several of the arms are seen to bifurcate again on 

 the fifth piece and twice to three times more at various distances above, while 

 they all gradually decrease in thickness with each bifurcation until they be- 

 come much attenuated, though the pieces of which they are composed main- 

 tain their length to such a degree that those of the smaller divisions are near- 

 ly twice as long as wide. 



Surface of body plates slightly beveled at the sutures and more or less 

 roughened by small ridges or nodes, which on the subradial pieces present 

 the appearance of nearly continuous, radiating, somewhat nodulous ridges, 

 while those of the first radials have more the character of irregularly disposed 

 nodes. 



Length of body below the top of first radial pieces, 0-40 inch ; breadth of 

 same aijout 0-64 inch ; length of arms from their origin on the last radials at 

 least 2 inches and perhaps a little more. 



This species seems to be more nearly allied to specimens in Mr. Wachs- 

 muth's collection that have been identified with Poteriocrinus Barrisi, Hall, than 

 to any other form with which we are acquainted. It differs entirely, however, 

 in its sculpturing, that species having its body plates marked with numerous, 

 rather fine, thread-like, radiating costte. The arms, however, are more similar 

 to those of our species, though they are rather stouter below in the latter. 



We have not had an opportunity to see the type of Poteriocrinus Barrisi, but 

 the form in Mr. Wachsmuth's collection, referred to that species by all the 

 Burlington Geologists, is a true Cyathocrimis, or more properly Cyathocrinites. 



Locality and position. — Lower division of the Burlington beds (Lower Carbo- 

 niferous) at Burlington, loAva. Mr. Wachsmuth's collection. 



Genus BARYCRLNUS, Wachsmuth, MS. 



(finpug-, heavy; zo/Vnv, a lily ; in allusion to the ponderous nature of the plates 

 and arms.) 

 Amongst the various American Carboniferous species that have been re- 

 ferred by different authors to the genus Cyathocrinus, there is a group of spe- 

 cies which, although agreeing with that genus almost exactly in the number and 

 arrangement of the pieces composing the body below the top of the first radials, 

 that still differs in several rather strongly-marked characters. In the first 

 place, these species are all more robust,* and have distinctly thicker and more 

 ponderous plates and arms than in the typical forms of Cyathocrinus. They 

 also differ in generally having a more or less developed, quadrangular subanal 



* Some of thera attain the gigantic size of more than 3-25 inches in breadth of body. 



[Dec. 



