LKCANOCRINIDAE 155 



Homalocrinus liljevalli n. sp. 



Plate VI, figs. 13-15 



A small species. Crown subglobose, widest about the upper IIBr, where 

 height to width is 1 to 1.8; at IAx, 1 to 2.4; expending broadly from base to IAx, 

 with spread of calyx 1 to 2.4. Side outline convex; base broadly truncate. 

 Rays deeply rounded and heavy looking. Surface smooth. Maximum crown, 

 19 mm. high by 18 mm. wide; base, 6 mm. 



IBB large, wholly or partly enveloping BB and RA. IIBr 2 or 3; IIIBr 

 2 to 4; ramules above this mostly on second or third Br. Height to width of Br 

 about 1 to 2. Main arm trunk bearing five or six ramules before infolding, the 

 lower one half as large as the main arm, and branching once or of tener. Arms 

 all deeply rounded, not closely abutting, and not tapering rapidly; their plates 

 convex leaving interbrachial spaces relatively much depressed. Anal x not 

 specially different from first iBr in other areas, except for small truncation to 

 meet post. B. First iBr large, obtusely angular above and followed by double 

 series of two to four ranges of small plates, filling the interradius; illBr usually 

 present. Tegmen composed of smallirregular plates forming a pliant disk, with 

 five large oral plates not in contact surrounding a central mouth, and ambulacra 

 passing out between them and branching to the ten main arms. Column 

 unknown. 



The discovery of the tegmen in a fragmentary specimen of this species has been men- 

 tioned in the generic discussion. This important fragment did not belong to any species 

 known at the Riks Museum, and I was at a loss where to place it until I received from 

 Mr. Liljevall a second figure (PI. VI, fig. 15a) giving a side view of the rays. Then I saw 

 that it was identical with two very good specimens of an undescribed species from Gotland 

 which had been in my possession for several years ; I am thus enabled to illustrate the species 

 very thoroughly. It is beautifully distinct from H. parabasalis. There is a certain heaviness 

 and lack of definite taper to the arms which gives it an entirely different aspect; while the 

 generally shorter intervals between the ramules, and the double rows of small interbrachials, 

 afford tangible structural grounds of distinction. The latter character is constant in the three 

 specimens, and as my second specimen is quite small we may conclude that it is not a matter 

 of individual growth. In this species finally we have an evident convergence in the arm struc- 

 ture of Calpiocrinus and Homalocrinus, and at the same time confirmation of their generic 

 distinctness. The lower ramule of the primary dichotom, which is here quite large, gives off 

 one or two lateral sub-ramules ; this can be seen on the two inner ramules of the original of 

 figure 13a, where the third and seventh brachials are axillary. On the other specimen, figure 

 14a, bifurcation can be seen at the second brachial. Figure i^a-h has the Calpiocrinus base 

 with the infrabasals covering everything but the apex of the posterior basal, so of course no 

 radianal is to be seen there; but the other specimen, figure 14, is less developed in that way, 

 the basals being well exposed and slightly unequal. In addition to this the infrabasals are 

 broken away, leaving the lower sloping faces of the basals open ; and here we see the radianal 

 fully developed in the position where we should expect to find it. This, I think, must be 

 accepted as proof to justify holding this species under Homalocrinus, but with an evident 

 tendency toward the other genus. 



Types. The type specimens for this species are those of figures 13 and 14 in the 

 author's collection, and of figure 15 which is in the Riks Museum, Stockholm. 



Horizon and locality. Silurian, Wenlock Group, horizon d; Wisby, Island of Gotland. 



