KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:0 2. 79 



being bounded as follows, — (1) by articular facet, with a slight. convex curve, 4.75 ram.; 

 (2) by r. ant. R', with convex curve, 4.3 mm.; (3) by left B (i. e. the hinge-line), 3.25 

 min.; (4) by 1. ant. \l\ 6 mm.; (5) by 1. post. K, 1 mm.; (6) by 1. ant. R s and the angle 

 of ant. IBi'i, together forming a convex curve of 4 mm.: the extreme height of this plate 

 is 8.8 mm. In b this plate is similar in shape; the measurements, however, are rather 

 more, the extreme height being 10.3 mm., but the specimen is not well enough preserved 

 to give them with certainty. In a, 1. post. R is distorted, but in h it is bilaterally sym- 

 metrical with ant. R. Of the above-mentioned sides No. 1 is at right angles to No. 6, 

 and forms an obtuse angle of 130° or more with No. 2. 



r. ant. R' is roughly four-sided, being bounded as follows, — (1) by ant. R, a 

 convex curve, 4.3 ram.; (2) by ant. IBi^, a soinewhat sinuous line, 3 ram.; (3) by T-piece 

 and possibly by a part of x, a slightly concave line, 2.6 rara.; (4) by stem-facet and r. 

 ant. B, an irregularly convex curve, 5.25 rara. R' which corresponds to this plate, is in a 

 soinewhat distorted. In l> the plates have similar relations, but are not well enough pre- 

 served to be measured. 



The r. post. R A and r. ant. R* are fused into one plate (T-piece): of this only a 

 small portion is seen in a, owing to the preservation of the stein; in h likewise it is 

 difficult to make out, since the specimen is fractured at this point. It appears, however, 

 to have been a low wide plate, resting partly on the infer-radials, and slightly excavated 

 between thera for the reception of the stem and of the lower and posterior part of the 

 base. On its upper si de the T-piece is concave and supports x. 



Anal structures: In this fainily it is convenient to treat of these in immediate 

 connection with the radials. x is a curved plate, roughly quadrangular; in a it is about 5 

 min. wide below, slightly less above, and 2.8 ram. high. It rests mainly on the T-piece, and 

 by its slightly truncate lower angles on the radianal and r. ant. R'; the details are, how- 

 ever, obscured by fracture and distortion. It is followed by a similar, curved and massive 

 plate, which in a is 3 mm. high, about 4 mm. wide below, and 3 mm. wide above. The 

 ensuing plate is absent from a, but its shape may be gathered from C. tenax (p. 89) 

 where it is well seen. Instead, a shows the sutural surface on which this plate rested; in 

 outline this lvsembles the section of an ossiele of the 1. ant. ärra, but is a trifle wider 

 and the groove is not so deeply cut; its angles too appear to have been truncate, pre- 

 sumably for the attachment of the smaller ventral plates of the tube. The sutural sur- 

 face is slightly concave and covered with minute granules; its outer edges are gently 

 rounded off. 



Arms: L. ant. is much stouter than any of the branches of the other arms; it is 

 apparently simple; in other words, neither specimen shows any trace of armlets or pinnules 

 or of their attachment. In a nine ossicles are preserved. IBr x is 2.2 mm. high; its width 

 at the base is 5.5 mm.; it widens upwards to 6.2 mm. and again eontracts to 4.75 ram.; 

 it is thus hexagonal and abuts by its lower outer sides on the radials and primibrachs of the 

 adjoining rays. The subsequent ossicles decrease gradually in width from 4 mm. to 3.5 

 mm. half-way up, and at the distal end, 2.75 mm. The heights of the ossicles are — for 

 the second primibrach, 2.9 mm.; for the fourth, 3.9 rara. The depth grades from 4 ram. 

 in the proximal region, to 3 mm. in the distal region. The ossicles are very slightly 



