24 PROCEEDINGS OF THE ACADEMY OF 



Arras two from each ray, rather long, rounded, and tapering ; very stout 

 below, where they are composed of thin (short) wide pieces, the first two of 

 which, in each pair of arms, are joined together at their inner ends ; above 

 these the arms of each ray diverge more or less from each other, and throw 

 off alternately on each side stout armlets from every second piece. Arm 

 pieces above the wide ones at the base, somewhat longer in proportion to 

 breadth than the latter, and more or less wedge formed, with each a little 

 pinched or angular ridge or projection on each side, ranging transversely to 

 the arms. Armlets stout, about eight to nine on each side of each arm, near 

 half as thick as the arms just above the points where the two connect : com- 

 posed of pieces of nearly the same form as the arm pieces, but generally show- 

 ing a slight disposition to become a little zigzag, and, at least some of them, 

 throwing off alternately on each side a series of smaller secondary armlets, 

 exactly as they are themselves given off from the main arms. Secondary 

 armlets showing a slight zigzag appearance, from the greater thickness and 

 prominence of every second piece on opposite sides, so as to appear as if they 

 may give off a tertiary series of armlets, or pinnulse, though the specimen does 

 not show these if they exist. 



Column very stout, nearly round, and composed, at least for about three 

 inches or more below the base, of alternately thin and somewhat thicker 

 pieces, the latter of which project outward a little beyond the others, and 

 show a slight disposition to become nodular, or irregularly thickened on the 

 edge. Internal cavity large, with an obtusely pentagonal section. Longitu- 

 dinal sutures, dividing the column into five sections, partly anchylosed, but 

 still visible. 



Height of body, about 1 inch ; breadth, about 1-70 inches ; length of arms, 

 3-80 inches ; thickness of do. at the base, 0-40 inch ; thickness of column near 

 base, 0-60 inch. 



This fine large species seems to be most nearly allied to D. Thomte, {= Cya- 

 thocrinus Thomse, Hall), from the Warsaw Limestone, but differs in having the 

 impressions at the comers of its body plates, and the ridges between the same, 

 greatly more strongly defined, and its arms much stouter, and more rounded 

 below. Its column is also proportionally thicker, with a more obtusely pen- 

 tagonal internal cavity. The typical specimens of the B. Thomce, which are 

 now before us, are not in a condition to show much of the arms, but as far as 

 they can be seen, they seem to be proportionally more slender, and we can 

 scarcely doubt that they will show other corresponding differences in the de- 

 tails of their structure, when better specimens can be compared. We have 

 ascertained, however, that the arm-pieces of the typical specimens of B. 

 Thomse have on their sides little pinched-up prominences, as in the species 

 here described, which character was not mentioned in the description of that 

 species. 



The peculiarity of having the corners of the body plates impressed so as to 

 form large ridges on the plates is very common in this group, but it differs in 

 degree, or otherwise, in the various species, presenting corresponding differ- 

 ences in other parts. It is more strongly defined in the species here described, 

 and the ridges more angular than in any other known to us. This species is 

 also the first of the group in which we have clearly seen secondary armlets 

 springing from the sides of the larger ones given off from each side of the 

 arms; but since seeing this character in this species, we think we have been 

 able to detect indications of it in others. 



We hope those who may not be disposed to admit the genus Barycrinus as 

 distinct from Cyathocrinus, will at least write the name of this species Cyatho- 

 crinus (Barycrinus) spectabilis. 



Locality and position. Otter Creek, Jersey County, Illinois ; from the St. 

 Louis Group of the Lower Carboniferous. 



Cyathocrinites ? poterium, M. and W. 



Body small, depressed-subglobose, somewhat flattened below and con- 



[April, 



