FOSSILS OF THE BURLINGTON GROUP. 365 



of the pieces composing the walls of the body below the arms, nor in 

 the vault and its elongated central or subceutral tube, though its second 

 radial pieces generally diifer in being proportionally shorter and quad- 

 rangular, instead of hexagonal or pentagonal. One of the most obvi- 

 ous differences, however, consists in the arrangement of the brachial 

 pieces and adjacent parts, which in Batocrinus form a nearly or quite 

 continuous series all around, instead of being grouped into five protu- 

 berant lobes, separated by more or less wide and deep interradial and 

 anal sinuses. Again, in Batocrinus the arms never bifurcate as we often 

 see in Actinocrinus, all the divisions of the rays taking place in the 

 walls of the body below the brachial pieces; while the arms, (which in 

 all cases yet known, with one exception, spring singly from each arm- 

 opening), are generally much shorter in proportion to the length of the 

 proboscis, which often projects from one third to one-half its entire 

 length beyond the extreme ends of the arms. Another difference is to 

 be observed in the surface of the body plates, these pieces never being 

 sculptured or ornamented with radiating costse, as is often seen in Ac- 

 tinocrinus, but merely even, more or less tumid, or tuberculiform. The 

 vault pieces in Batocrinus are also generally tuberculiform, or sometimes 

 produced into short spine-like projections ; but even where they assume 

 the character of spines they never have the regularity of arrangement, 

 nor do they ever attain the length we often see in Dorycrinus and Am- 

 plioracrinus. The species of Batocrinus also present a much greater 

 diversity of form than we see in ActinocrinuSj since we find amongst 

 them every variety of shape, from globose to turbinate, biturbinate, 

 pyriform, discoid, and even, in some rare aberrant types apparently be- 

 longing here, a conical or stelliform outline. 



The species of this genus may be variously grouped to facilitate their 

 study, into sections and subsections, based upon their differences of 

 form, and other more or less marked peculiarities, but for the present 

 we merely propose to give a general list of them, and to notice a few 

 types that we have elsewhere included in this group, but which we are 

 now rather inclined to think may yet be found to be entitled to more 

 prominence than has generally been supposed. These are the forms for 

 which the names AlloprosaUocrhiHft (= Conocrinus, of Troost's list), 

 and Eretmocrinus. Lyon and Casseday, were proposed. 



The first of these we only know from specimens consisting of the 

 body without the arms or other parts. Its most striking peculiarity, 

 so far as yet known, consists in its remarkable conical form, the body 

 being nearly or quite flat below the arm-bases, which are at first directed 

 out horizontally, and then curve up; while the vault, which forms the 

 whole visceral cavity, is produced upward in a conical form, so as to 

 pass rather gradually into the central or sub-central tube, or so-called 



