LECANOCRI'NIDAE' 171 



radianal, and a truncate anal plate. But the arms are of a heavy, elongate, divergent type 

 wholly foreign to the Lecanocrinidae generally ; upon arm structure alone it would stand next 

 to Lithocrimis, with heterotomy less regular than in that genus. Considering the nature of 

 its calyx, and that it has large infrabasals, forming upright pentagons in the calyx wall as 

 typified by Lecanocrinus, the genus is perhaps better placed in this family than in the Sageno- 

 crinidae. It also has a short, strong stem with encrusting root, further indicating its affinities 

 to be with shallow water forms like Calpiocrinus and Homalocrinus. 



The interbrachial structures are finely shown by the enlarged detail from the type speci- 

 men (PI. IX, fig. lb), and also clearly indicated in another good specimen (fig. 2a). Angelin's 

 principal figures were based upon a single specimen which was badly crushed at the anal side, 

 the posterior basal being pushed under the radial to the left. His figure (pi. 28, fig. 2) takes 

 no account of this, but represents the posterior side with its basal of the same form as the 

 others, and not touching the anal x at all. My new figure, ic on Plate IX, shows very clearly 

 what the arrangement of the plates must be, while the fortunate discovery of two other 

 specimens of this rare form removes all doubt upon this point (PL IX, figs. 2b, 3). In addi- 

 tion to these figures, Mr. Liljevall has made two more enlarged drawings from Angelin's 

 original of F. obesus, giving important information as to the anterior ray, and also a series 

 of enlarged figures of the fragment figured by Angelin on plate 26, figures 6, 6a, as F. divari- 

 catus. which proves to belong to the same form ; this is a specimen of much importance, 

 affording complete confirmation of the anomalous arm arrangement indicated by the other 

 specimens, and also disclosing the structure of the tegmen (PL IX, figs. Afi-e). 



The unequal development of the rays in the only known species is a most peculiar feature 

 of this genus. I have not included this character in the generic diagnosis, because the separa- 

 tion is perfectly valid without it, and whether this structure is correlated with the other 

 generic characters or only represents a freak exhibited by a single species may as well be left 

 an open question for future discoveries to settle. There is no doubt that it is perfectly con- 

 stant in the four well-marked specimens which are known ; being in no sense a mere indi- 

 vidual irregularity or abnormality, but representing a modification of pentamerous symmetry 

 in a definite way. The anterior and two posterior rays are enormously enlarged, so that they 

 constitute about five-sixths of the brachial equipment — the two antero-lateral rays being 

 dwarfed to a condition of relative unimportance. This may be seen as to the proportional 

 size of these rays at the base by comparison of figure le, from the large anterior ray, with 

 figure ia, showing the right anterior ray of the same specimen, scarcely more than half the 

 size. Figure 2a also gives a good idea of the disproportion between the right anterior ray 

 and the adjacent anterior and right posterior rays which completely overshadow it. This 

 disproportion is, however, really much greater than the mere difference in the width of the 

 primibrachs at the base of the respective rays would indicate ; for the two smaller rays in 

 every case are folded under the larger ones, and evidently had little chance to grow. The 

 result is shown best of all by the figure of another specimen in which the five infolded rays 

 are seen at one view (fig. 4b). Each of the large rays has by its bifurcations produced four 

 main branches, each fully equal in size to either of the two smaller rays, so there can be no 

 doubt that when fully spread out the combined food-gathering surface of the three large rays 

 would be at least five or six times that of the two smaller ones. 



This kind of irregularity in the rays has not been observed before among the Crinoidea 

 Flexibilia, although it is not an uncommon occurrence in the Camerata, as evidenced by the 

 varying number of arm openings. The mode of variation does not seem to follow any fixed 

 rule, except that the increase in number usually occurs first in the posterior rays and after- 

 ward in the lateral ; the anterior ray usually remaining the longest unchanged. In Agarico- 

 crinus, where the simplest form has two arms to each ray, we find successive modifications in 



