364 PALAEONTOLOGY OF ILLINOIS. 



outer brachial pieces of the rays on each side. There is 

 also usually a small interaxillary piece between the secon- 

 dary radials of each ray, but it seems never large enough 

 to extend down so far as to truncate the upper angle of any 

 of the third primary radials. 



Arms stout, increasing a little upward for a distance of 

 two and a half inches (as far as they can be seen in the 

 specimen), each passing directly into a double series of very 

 short pieces, from their origin on the last brachial piece. 



Surface of body plates merely finely granular where not 

 worn, slightly convex, with shallow indentations at their 

 corners. Vault unknown. 



Hight of body to the top of tertiary radials, 0.75 inch ; 

 breadth, about 1.33 inch ; breadth of arms two inches above 

 their bases, 0.20 inch. 



This species is related to 8. (Physetocr.) subventricosus, McChesney 

 (sp.), but differs in having its body much more rapidly expanding, and 

 proportionally wider above, while its tertiary and brachial pieces curve 

 much more strongly outward. It also differs in the relative size and 

 form of its second radial pieces, which are proportionally smaller, and 

 generally quadrangular, or only with the upper lateral angles slightly 

 truncated, instead of being larger and regularly hexagonal. Its arms 

 are likewise stouter than those of McChesney's species, judging from the 

 brachial pieces seen in specimens of the latter, while it has one or two 

 arms more in each of the posterior rays. Its surface markings are also 

 different, but this is a very variable character in this group. 



Locality and position Lower beds of the Burlington group. Lower 

 Carboniferous. No. 58 of Mr. WACHSMTJTH'S collection. 



GENUS BATOCBINUS, Casseday.* 



FROM deference to the most generally prevalent opinions of paleon- 

 tologists, we have elsewhere included Batocrinw as a sub-genus under 

 Actinocrinus, though we did so with a protest, stating that we were 

 strongly inclined to view it as a distinct genus. Our recent study of 

 Mr. WACHSMUTH'S extensive collections has still more decidedly im- 

 pressed us with the necessity for separating these groups generically. 



As we have in other places stated, the genus Batocrinn$ presents no 

 essential difference from Actinocrinm in the number and arrangement 



*Proceedings Acad. Nat. Science. Philadelphia. 1869 p. 350, et. seq. 



