72 F. A. Bather — Ordovieian Crinoids. 



resemblance to the stem of G. hasalis, M'Coy, but not enough to 

 warrant the use of the name. The two other specimens are certainly 

 not Glyptocrinus. The rocks just described are part of the " Middleton 

 Group," which is the middle of the Meadow Town Series, which is 

 the middle of the Ordovieian (see Prof. C. Lapworth. "Preliminary 

 Note on the Ordovieian Eocks of Shropshire," Geol. Mag., Dec. III. 

 Vol. IV, p. 78, 1887). Older writers call them Llandeilo Beds. 



Description. — The two specimens studied are in a dark, fine- 

 grained, micaceous sandstone, and are in the form of moulds, the 

 calcareous suhstance of the orinoid having been dissolved. They 

 are therefore best studied from wax squeezes. 



Specimen A. 



The lower, or proximal, part of the Dorsal Cup is wanting. Of 

 the basals (BB) a portion only is preserved. The radial s (RE) 

 appear to alternate regularly with the basals, and do not appear 

 to be horizontally bisected. They are about as wide as high, 

 depressed towards the iuterradial sutures, and projecting slightly 

 in the median line towards the articular facet. Tbe facet occupies 

 the greater part, but not quite all, of the width of a radial, so that 

 the arms clearly are separate from one another ; in other words, the 

 crinoid is an Inadunate. 



Of the Arms, four are visible. They appear to dichotomize pretty 

 regularly, though the dichotomy is only seen clearly in the second 

 from the left. This, which I take to be the left posterior arm, 

 has brachials as follows : IBr, 5 ; IIBr, 8-8 ; IIIBr, 8-10-8-3 

 (preserved, ends not seen) ; IVBr, only traces seen. The next 

 arm, i.e. the second from the right, appears to be the right posterior 

 arm, since the first primibrach appears to be axillary, and supports 

 a branch on the left, which I take to be the anal tube ; of the right 

 branch only three more brachials are preserved : in other words, 

 four primibrachs in all are preserved. The arm on the right of the 

 specimen appears to be the right anterior arm : it is difficult to 

 decide whether the small branches that appear to be given off from 

 its left side may not really be a single branch seen from the inner 

 surface, at least for a distance of six ossicles, after which there are 

 plainly two branches. In all the arms the proximal primibrachs 

 seem rather wider than the distal primibrachs. Each brachial seems 

 to be slightly wider at its distal end, so that the arms tend to have 

 an imbricated appearance. 



The Anal Tube (t in Fig. a), arising from the left upper slope of 

 IBi-j, is thinner than the arm-branches at corresponding levels, 

 and shows no signs of further dichotomy. Its exposed side shows 

 a longitudinal series of rounded ossicles, of similar appearance to 

 the brachials. The distal end is not seen. 



Measurements : total height of specimen, 9-0 mm. ; width of cup 

 at level of top of BR, about 1-5 mm. 



Systematic position of Specimen A. — The relation of arms to cup 

 shows that tins specimen belongs to the Inadunata. The absence 

 of the base does not enable us to refer it to either Monocyclica or 



