BATOCEINID^. 365 



Megistocrinus, of which a species may possibly exist in the Mountain Lime- 

 stone of England — and are replaced by the Actinocrinid^. This is also 

 the case in the western territories of the United States. At Lake Valley, 

 New Mexico, among many hundred Camerate Crinoids collected from the 

 horizon of the Burlington group, we found only one or two straggling 

 Batocrinoids. 



The genera for which this family is proposed, with the exception of 

 Compsocrinus, have been heretofore referred by us and others to the 

 Actinocrinidse, and most of the species were originally described under 

 Actinocriniis. Even the genus Batocrinus was not accepted by the earlier 

 writers. This was no doubt largely due to the fact that Casseday in 

 describing the genus overlooked the arrangement of the plates of the anal 

 area, which, as we think, forms the principal distinction between the two 

 groups. He only alluded to the meeting of the distichals and palmars over 

 the interbrachials, and the separation of the latter from the plates of the 

 ventral disk. The importance of the structure of the anal area was pointed 

 out by us in the Revision, Part IL, p. 139, when we recognized the genus 

 Batocrinus, but at that time we only made it the type of a subgroup under 

 the Actinocrinidffi. 



As now defined, the Batocrinidse are by far the largest family of the 

 Camerata, and they have a greater stratigraphic range than any except 

 the Rhodocrinidse, — appearing first in the Hudson River group of the 

 Lower Silurian, and continuing into the Warsaw. The family consists of 

 eighteen genera, of which twelve, so far as known, are restricted to America, 

 and six to Europe ; while Periechocrinus and Megistocrinus occur on both 

 sides of the Atlantic. Of these genera two hundred and three good species 

 have been recognized, — fifty of them coming from Europe and one hundred 

 and fifty-three from North America. 



There are in Europe two other genera which probably ought to be 

 placed in this- family, — Poli/peltes Angelin, and Spyridiocrinus Oehlert ; but 

 as the arrangement of the two or three proximal rings of plates in the calyx 

 cannot be made out in the specimens, they may possibly belong to the 

 Melocrinidse. 



We have subdivided the genera of this family into two sections, which 

 will considerably facilitate identification, viz. : — 



