84 F. A. BATHEBj ORINOIDEA OF GOTLAND. 



The 1. post. 1{ is bilaterally symiuetrical with this. In both, side 1 is a1 right angles to 

 side 6, and at an obtuse angle of llö° to side 2. 



The r. ant. R' is 5-sided, being bonnded as follows. — (1) by ant. 1J, with a convex 

 curve, 3.25 rum.; (2) by IBr, and IBr 2 of ant. ann, a slight convex curve, 4 mm.; (3) 

 by T-piece and sometimes a part of x, a slight convex curve, 2.-25 tum.; (4) by stem- 

 facet. a concave curve, 1.2 mm.; (5) by r. ant. B, a convex curve, 4 inni. Sides 

 1 and 2 in sonie cases form a continuous curve. R' is bilaterally symmetrical with 

 this plate. 



The T-piece is concave below, with a width of 2.75 mm., and concave above, with 

 a width of 5 mm.; its least height is in the middle and is about 0.75 mm. Its sides 

 rest on R' and r. ant. \l>. 



Anal structures: x is shaped as in C. gotlandicus, but is lower in proportion. 

 Its width below is 5 mm.; its height is 1.75 mm. It rests on the T-piece and mav also 

 abut by its corners on R' and r. ant. R*. This appears to be more the case on the radi- 

 anal side. 



A similar plate, apparently 3.2 mm. wide below and narrowing above, follows on x; 

 its upper part and the ensuing plates are not clearly shown in any specimen, since they 

 were covered by the arms when in the closed state. 



Arms: 1. ant. is not very much stouter than the larger branches of the other arms, 

 but this is due to increase in the size of those branches, not to decrease in 1. ant. arm. 

 It is apparently simple. Its total length was 24 mm. In one specimen 8 ossicles are 

 preserved, but there must have been one more, and only one. The first brachial is hexa- 

 gonal; it is 2 min. high; it rests on the upper half of ant. R by an articular surface 

 5.5 mm. wide; the articulation is not shown; it abuts by its lower sides on the large ra- 

 dials, and by its upper sides on the first «Br of the primaxil arms; its upper articular 

 margin is slightly convex, with a width of 4.5 min.; its articular surface has been exposed 

 by dissection in one specimen and is slightly granular, and in plan is like the sector of 

 a circle with a sharp reentrant angle at the apex; this shape is due to compression by 

 the arms. The second brachial is 3 mm. high, 4 mm. wide. The third brachial is 3.5 

 mm. high, 4.4 mm. wide. Succeeding brachials may attain a height of 5 mm., but usually 

 they decrease gradually both in height and width, the decrease being very rapid in the 

 last two. Neither their articular surface nor a section is clearly seen. The section is 

 apparently more transversely elliptical than in C. gotlandicus, with a somewhat flattened 

 ventral surface and a very narrow ventral groove. 



The ant. and 1. post. arms follow the ordinary law of branching; but the appearance 

 produced is very different to that of C. gotlandicus. In the ant. arm there are 2 primi- 

 brachs: IBrj is low and wide, almost crescentic; IBr 2 or lax rests on IBr x and abuts on 

 ant. R by its right corner, and on r. ant. R s by its left eorner; its right upper slope 

 supports the primaxil-arm, and its left upper slope Ilax. There are visible ö main-axils, 

 but no specimen shows more than 4 axil-arms. In one specimen Illax of 1. post. arm 

 is rather thicker than the others and appears to be double; otherwise the main-axils follow 

 on one another as usual. The concave articular facet does not occupy the whole of the 

 left upper slope of each main-axil, but for about their upper thirds the main-axils abut 



