OARADOCIAN CYSTIDEA FROM GIRVAN. 



393 



8 139. Measurements of the Brachial Appendage in millimetres are : — 





Length, 



Proximal Width. 



Distal Width. 



G80 



21 



33 



1-6 



G102 



26 



4-9 



2-0 



G84 



21-5 



2-3 



•4 



G120 



ca. 23 



3-6 



•7 



G92 



20 + 



4-6 



2-9 quite in- 

 complete 



G98 



ca. 24 



4 



1-8 



G95 



34 



4-2 



•9 



Few of these can be regarded as completely preserved. The amount missing at 

 the distal end may be roughly estimated by considering the diameter of the remainder. 

 Thus Gr84 is nearly or quite complete, and G92 broken off relatively low down. 



In G80 and Gl02 the height of the theca is almost exactly equal to the length 

 of the appendage preserved. In G 84, where the appendage is most complete, 

 the theca has a height of only 13 "6 mm., less than two-thirds the length of the 

 appendage. 



§ 140. The Antibrachial Process is so pronounced a feature of this species that 

 it calls for separate description. Traces of it are frequently to be seen, but most 

 specimens are so broken that the two processes — brachial and antibrachial — are rarely 

 found in association. G80 was taken as holotype, because it shows both processes 

 clearly (PL IL figs. 11, 12). Here the antibrachial is well defined and springs almost 

 abruptly from the theca; it is 9*5 mm. long, 3'4 mm. wide, and is composed of about 

 four columns of plates, which diminish in size distally. In Gl20 also (PI. II. fig. 10) 

 the process is very distinct: ca. '9 mm. long, 3*7 mm. wide, and composed of regular 

 hexagonal plates, which, except at the extremity, are 2 mm. long and 2 '4 mm. wide. 

 In G82 (PI. II. fig. 13) the process is still more prominent, and is curved upwards, so 

 that it and the brachiole look like a pair of incurved horns ; though not quite complete, 

 it attains a length of 17 mm., with a width decreasing from 6 '5 mm. to 3*8 mm. ; the 

 plates appear to be hexagonal, about 3 mm. long and 2 mm. wide, that is to say, 

 elongated in harmony with the length of the process. 



§ 141. The evidence for the position of the Vent in the genus as a whole depends 

 so largely on the facts afibrded by this species, that the evidence must be given in 

 detail. 



In a number of specimens, at the lower edge of one of the proximal lobes of the 

 theca, there is an appearance as of several small, closely -set, imbricating plates, their 

 long axes tangential to the outline. This is seen in the holotype (G80), also in G69, 

 G70, G79, G83, G88, G90 (two individuals), Gl02, Gl06, GllO, Gll2, Gll5, 

 and Gr28. There are very few specimens presenting both sides of both lobes that 

 do not show this appearance (see especially PI. II. figs. 23-25). 



