KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:o 2. 77 



would be absurd for one who bas not worked över all the material to make any state- 

 nieiits with regard to tbem. 



Many apparent differences are due to the extent to which the arms are closed, or 

 the angle that the crown happens to be making with the stem; but these should mislead 

 no cautious naturalist. 



The Gotland species may be divided into two main groups: one containing all spe- 

 cies with the arm-branching conforming to the general Family type; the other containing 

 only C. pinnulatus, in which the arm-branching presents certain deviations from that 

 type. The firat group may again be divided into species with two primibrachs, and spe- 

 cies with one primibrach, the latter division containing only C. nitidus. From the division 

 with two primibrachs may at once be separated C. interpres, which in the shape of its 

 cup and of its arm-ossicles totally differs from all other species of this division. The 

 remaining species form a closely connected evolutionary series, leading from C. gotlandicus 

 up to C tenax: the extremes of the series are far apart, but the connecting species are 

 so numerous that their separation and diagnosis has been a matter of no small diffieultv. 

 Further discoveries may degrade some of these species to the rank of varieties; meanwhile 

 their discrimination undoubtedly enables one better to appreciate a most interesting chapter 

 in Crinoidal evolution. 



Calceocrinus gotlandicus. 



(Plate III, tigs. 83—97.) 



1878. Chirocrinus gotlandicus, Angelin, Iconographia, p. 22, Tub. XVI, figt*. 6, 7, 8, 9, not figs. 10, 

 11, 12, 13, 14. 



Emended diagnosis. 



Proportions of cup are, — height 1; widtli 1.13; width at hinge 1.15; thickness 0.84. 

 Cup seen from 1. ant. radius oblong, with slight constriction half-way up. 1. ant. R* and 

 \l l separated. T-piece low, wide, biconcave; rests by its corners on the infer-radials. 

 ,c not quite twice as wide as high; rests on T-piece and on infer-radials. 1. ant. arm 

 much stouter than any of the branches of the other arms; apparently simple. Ant. and 

 1. post. arms have mainaxils up to Vax, and probably not many more. IBr 2. Axil- 

 arms follow the normal type; adanal />'Br and ;'Br rather stouter than other arm-bränches; 

 all axillaries widen above, but are liardly at all nodose; abanal branches and all after ;l'>r 

 are compressed laterally. Hinge with well-marked cross-processes. Shagreen ornament 

 well marked. Curvature of stem-ossicles very slight. 



As type-specimen of this species is taken the specimen represented in the earlier 

 figures to which Angelin attached the name C. gotlandicus (No. 64 RM). This alone, of 

 all the twelve specimens known to Axgelin, agrees with his diagnosis and measurements. 

 In one point only is there a discrepancy: the specimen has no stem preserved, and in the 

 only other specimen of the species the stem is not partieularly fine, nor are its ossicles very 

 distinctly curved (No. 67 EM). The latter specimen was mostly obscured by matrix, 



