KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:<) 2. 135 



portion, c 2 . On the interiör (fig. 212) c 2 is not seen; for each c 2 lies between two c's 

 of the opposite side, and is separated from the ventral groove by the swelling and apposi- 

 tion of their inward portions (tig. 211). On the interiör, however, there are seen small 

 round ossicles (/), each of which bears to the internal surface of its adjacent covering- 

 plate (/') rauch the same relation that c 2 does to the externa! surface. The inner piece, 

 i, does not, however, extend beyond the median line, but abuts on a process of the op- 

 posing c 1 . The edges of the ventral groove are marked off into concave, subcrescentie 

 facets for the articulation of the covering-plates: each of these facets has a median notch, 

 comparable to the notch in the articular facet of a primitive braehial. The articular por- 

 tion of c 1 is marked in corresponding fashion, viz., with a median depression or hole and 

 a slight sub-crescentic ridge outside it. The sides of c 1 are concave, for the reception of 

 the alternating c 2 ; while the distal end is also concave for the attachment of its own c 2 . 

 The sides of c 2 are convex. The elaborate articular surfaces were necessitated by the 

 great size and solidity of the plates, far exceeding that in any recent Crinoid; while the 

 median notch and hole suggest that each covering-plate had a well-defined branch from 

 the axial nerve. All the elements described were doubtless ambulacral, and the splitting 

 ii]) of the covering-plate into three parts may have been to facilitate motion. 



The primibrachs and secundibrachs number from 3 to 5. Subsequent series gradu- 

 allv increase in number. The dichotomy is traceable up to the sixth series. 



Anal struetures: x supports three plates of the tube, of which the middle one is 

 the largest. These tliree plates and all the more proximal plates of the tube are hexa- 

 gonal; but distally the plates become irregular in outline. The plates are a little smaller 

 in proportion than in C. longimanus; but, as in that species, they are very thick. They 

 are rather more warty, protuberant and rugose (fig. 214). No intima te strueture is vi- 

 sible, but the superficial rugosities have a radiating arrangement. In none of the (Jot- 

 land specimens have I been able to see any folding at the edges of the plates such as is 

 visible in an English specimen referred to this species. The tube is about half the length 

 of the arms or less; it is rounded and somewhat swollen above. 



The Stem is not preserved in the type-specimens a and b, with the exception of 

 portions of two ossicles in a. There is, however, in the Riksmuseum, a piece of stem in 

 conjunction with arm-fragments that are apparently of this species. This stem is of the 

 same character as the stems of the English specimens referred to C. acinotubus. From 

 their combined evidence we learn that the stem is round, composed of ossicles alter- 

 nating both in height and width, with a quinquelobate lumen, the diameter of which is 

 about '/ 3 that of the stem. The articular surface of each ossiele is radiately striated. The 

 base of the cup is often slightlv excavated for the top stem-ossicle. 



Ornament: In very well-preserved specimens a fine granulation may be seen on 

 the cup plates; this however, is usually worn off. In a few specimens there is a 

 slight ridge or fold of the ])lates parallel with their margins, and at a distance of 

 about 1 mm. from the suture, which may be compared with the ornament chai-aeteristic 

 of C. ra II ut iis. 



