on British Palceozoic Crinoids. 283 



A projection of the calyx and the arm-bases in connexion with 

 it is shown in fig. 3 of the same Plate. 



There are only two rows of plates in the calyx, which is 

 cylindro-conical in form, expanding slightly from below up- 

 wards. The basals form a complete ring and a very shallow 

 pentagonal cup, but little higher at the angles than at the 

 sides ; the sutures are nearly if not quite invisible as a general 

 rule. Fig. 4 (PI. XV.) represents the interior of this cup 

 as seen from above. The five radials which rest upon it are 

 elongated pieces with subparallel lateral margins, increasing 

 slightly from below upwards both in width and in convexity. 

 They vary considerably in size, some of them being axillary 

 and bearing two arms, while others are narrower and have 

 only one articular facet on the upper surface (PL XV. figs. 2, a, 

 2, J). In two specimens (PI. XV. figs. 1-3) four of the radial 

 plates are wide and axillary, so that the number of (primary) 

 arms must have been nine. In the third specimen, however 

 (PL XV. fig. 6), only three of the radials are axillary, corre- 

 sponding to eight primary arms ; while the two adjacent ones, 

 which bear but one arm each, are unequal in size (PL XV. 

 fig. 6, h). The articular facets for the attachment of the arms 

 are large and distinct (PL XV. fig. 6, a &^), and nearly hori- 

 zontal in position, so as to give a projecting lip-like appear- 

 ance to the upper and outer edges of the radials. They have 

 the same general form in all three specimens, although a 

 certain amount of variation is perceptible. The dorsal fossa 

 for the elastic ligament is narrow and crescentic, and lacks the 

 central pit, which is often so very distinct in other Crinoids. 

 Above it is the transverse articular ridge expanding around 

 the opening of the central canal, which is unusually large. 

 On the upper side of the ridge are large fossfe for the arti- 

 cular ligaments, which vary somewhat in shape in the diffe- 

 rent specimens. The muscular foss», in the few cases in 

 which they are discernible, are small and at a lower level than 

 the ligamental fossae, from which they are separated by 

 ridges. 



Two of the specimens have the lowest joints of the arms 

 preserved. They are small and irregularly cuboidal, with 

 nearly circular distal faces (PL XV. figs. 2 & 6). In the 

 best specimen the second and third brachials of three arms 

 are also preserved (PL XV. figs. 2, 3). Each joint has an 

 almost cylindrical shaft, with slightly expanded ends. Where 

 the first radial is axillary, the second brachial is not much 

 longer than wide ; but in the second brachial of the azygos 

 arm the length is more than twice the width. This may, 

 however, be merely an accidental difference ; for the three 



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