KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:o 2. 75 



radiculusi is due, at least in part, to the greater thickness of the ossicles on the outer 

 side of the curve, i. e. in the left anterior radius. There is however a curvature of the 

 ossicles themselves, especially, but not solely, in the proximal region, Avhich does not 

 appear to have been alluded to by previons writers other than Angelin, who probably 

 ineans tliis by the words »articulis curvis» applied to the stem of C gotlandicus. The 

 ossicles are so curved that a median elevation runs sagittally to the crown in the line of 

 the left anterior radius and right posterior radius. There is a corresponding depression 

 on the under side of each ossicle. This curvature may be detected in species of Ctisto- 

 erinus, but in thein it is verv slight; it becoraes more marked as the trne Calceocrinus 

 type is approached, and attains its maximum in the raost specialised forms of that genus 

 and in Halysiocrinus. In some species, e. g. C. tenax, the elevation has almost the aspect 

 of a median ridge. It is possible that there is here seen the nascent stage of such a ridge 

 as is found in the Platycrinidse and Bourgucticrinida\ If its effect was the same, as to 

 some extent it must have been, the motion of the stem, while facilitated in a transverse, 

 would be checked in a sagittal direction: thus the strain which would otherwise have been 

 continually put on the stem by the pendent crown must have been in great measure relieved. 

 The distal end of the stem is very rarely found in the CalceocrinidsB. Messrs. 

 WACHSMUTH and Springee 1 ) mention that the eolumn was often long and that they have 

 »followed it up to a foot or more without reaching the root*. The only tigure or descrip- 

 tion hitherto given of the attachment of any Calceocrinid is that of -»Cheirocrinus^ clarus 

 by Prof. J. Hall; 2 ) here the stem is attached by a branching root-expansion to the stem 

 of another crinoid, which latter. Prof. Hall considers, was probably living at the tirae or 

 otherwise the arms of the »Cheirocrinusi would almost have reached the sea-floor. The 

 stem as drawn is in fa et only 65 mm. long, while the length of the crown is about 55 

 mm. Under these circumstanees it seems advisable to draw special attention to new facts 

 brought to light by the specimen of Calceocrinus interpres from the Klinteberg. The stem 

 in the specimen is 44 mm. long, and is composed of 30 ossicles. The 20th ossicle from 

 the crown has a height of 1.5 mm. and a diameter of about 4 mm.; the remaining 10 

 distal ossicles do not lessen appreciably in height but gradually lessen in diameter, the 

 last 3 tapering off very suddenly, so that the stem looks verv like a common earth-worm. 

 There are no signs of cirri or root-expansion. The distal end of the stem was entirely 

 covered by matrix, so that its shape cannot be due to weathering after fossilisation. In 

 other genera such features have been explained as due to the severance of the animal 

 from its attachment and the gradual resorption of the distal stem-ossicles. 3 ) Thus ;i 

 crinoid hxed in youtli, either by .i root-expansion, or by its radica] or even its nodal 

 cirri, or b}' the coiling of its stem around some other object, may, in its niaturity, become 

 a temporarily locomotive or even an entirely free-swimming organism. It would not 

 however be (juite safe to assunie that we have, in the present instance, the normal mode 

 of ending of the stem. 



') Revision III, 281; Proc. 1886, p. 205. 



2 ) 15th Rep. N. Y. State Cab. Nat. Mist,, p. 11 C, Pl. i f, 17, 1862. 



3 ) See especiallv P. H. Carpenter On some new or little-known Jurassic Grinoids . Quart. Journ. fieol. 

 Soc, vol. XXX Vill, pp. :?1 — 33, 1882. 



