156 F. A. IJATIIEK, ORINOIDEA OK GOTLAND. 



Dorsal Cup rather small in proportion to arms, forming a fairly regular cone. 

 Measurements are, in one specimen, — height 5 mm., width at base 3 mm., width above 

 6.75 mm.; in another, - height 6 mm., width at base 3.3 mm., width above 9 mm.,- in 

 //■, — height 10 mm., width at base 6.25 mm., width above 16 mm. All the plates are 

 marked witli strong radiating ribs formed b)- the eoncrescence of granules. In this point, 

 however, there is considerable variation, which is increased by the extent to which the 

 specimens are weathered; for instance, the ornament is entirely obliterated in the specimen 

 figured in Tab. III, tig. 3 (tig. 276) as well as in that described as G. nudus (tig. 280). 

 The granular or moniliform character of the ridges is not well shown in Angelin's figures. 



IBB 3, unequal; very low and sometimes hardly distinguishable. In w the height 

 is 2.75 mm. In three specimens the small IB is in 1. post. radius (tig. 266), in two it 

 is in r. ätit. radius (tig. 265): and in yet another it does not appear to be in 1. post. 

 radius. 



BB 5, eqnal and hexagonal, except post. B. Greatest width and height both 2.5 mm.; 

 post. B 3 mm. wide and 2 mm. high. In w the BB are 5.25 mm. high and 5.5 mm. wide. 



b' K' 5; height 4.2 mm., height to bottom of facet 2 mm., width 4.75 mm., width 

 of facet 3 mm. The extent of the facet, however, varies considerably in the same indi- 

 vidual. In w the height to the bottom of the facet is 4 mm., the greatest width 8.75 

 mm. The axial canal is distinct. 



The Arms dichotomise regularly on a system cominori to this genus and Cyatlm- 

 crinus '). That is to sav, the series towards the middle of each dichotom contain more 

 ossicles than the outer branches; the outer branches, moreover, keep in line with one an- 

 other so that they have the appearance of main arms giving off armlets on their inner 

 sides. The brachials of the inner branches are, however, no smaller than the correspond- 

 ing brachials of the outer branches. In the folding of the arms that on the right of two 

 adjacent rays usually lies under that on the left. This, however, is not always the case; 

 in fact, owing to the length of the brachials, the arms often do not overlap at all in the 

 proximal half, and in the distal half the branches, being more free, are less regularly 

 disposed, so that a right may lie över a left in some or all of the rays. 



The brachials, as seen from the back, vary in their proportions from rather wider 

 than high to twice as high as wide; this is in undoubted specimens of the species and 

 not in those labelled (i. nudus. The backs of the brachials are sometimes rounded (tig. 

 267), sometimes with a flat obtuse angle (tig. 268), sometimes with a rather more acutc 

 angle the apex of which is truncate or rounded. The ossicles are slightlv compressed 

 laterally, and the sides are straight and high. The proportion of the dorso-ventral axis 

 is never very great but increases slightly towards the distal end of the arms. The os- 

 sicles are constrictcd about the middle and expand into a more or less pronounced ridge 

 distally. This ridge is more evident on the sides than on the back. Some specimens, e. g. 

 i hat tigured in Tab. III, tig. 3, show one or two minor ridges behind the distal ridge. 

 and these are almost contincd lo the sides of the ossiele (tigs. 276, 267 b). In one spec- 



') See detailed numbers given for Cyathocrinus acinotubus in Brit. "Foss. Crin. VIII . Ann. Mag. Nat. 

 I list., ser. 6, vol. IX. pp. 218, 21'.»: and for Gissocrinus elegans, infra, p. 160. 





