386 



DR F. A. BATHER. 



§ 101. Measurements of the Brachial Appendage in millimetres are : — 





Length. 



Proximal Width. 



Distal Width. 



E 16028 

 E 16026 



19-3 

 16 



2-3 



2 



•4 then rapidly tapering. 

 •9 so far as seen. 



§ 102. Vent. The sugar-loaf plate and adjacent small plates are depicted in 

 Barrande, pi. 27, ff. 20, 22, on the left of the stem, their relation to the brachial 

 appendage being uncertain. A similar appearance is presented by the original of 

 Bai!Rande, pi. 27, f. 1 (our PI. I. fig. 2), and less decidedly by Brit. Mus. El 6024. 

 But neither Barrande's figures nor our specimens clearly show any structure obviously 

 comparable with the vent of D. scotica. Repeated search and further preparation of 

 all the available material have at last revealed in E 16102 the arrangement drawn in text- 

 fig. 7 (p. 374). Here, between the sugar-loaf plate and the stem, are several elongate 

 plates converging towards a point on the margin below the sugar-loaf plate. That 

 point was, one can hardly doubt, the position of the actual vent. In both E I 6006 and 

 E 16 102 the thecal margin ascends from the sugar-loaf plate towards a rather angular 

 projection (§ 58). 



§ 103. Stem, measurements in millimetres : — 





Total Length 

 Preserved. 



Length of 



Proximal 



Region. 



Width at 



Proximal 



End. 



Width at 

 Distal End. 



Ratio of known 

 Length to Height 

 of Theca [viz.] 



E 16024 

 E 16025 

 E 16027 

 E 16006* 



16 

 35 



25 

 46 



7-4 

 7-5 

 8 

 8 



7 



6'7 



5 



21 

 1 

 2 

 1-5 



1-79 

 11 

 1-84 [ca. 



"17-5' 

 "19-5' 

 ■22-6' 

 25 





Owing probably to the irregular fracture of the quartzite, no specimen retains the 

 complete stem. It is therefore likely that the total length was normally quite twice 

 the height of the theca. 



§ 104. The Distal region does not diff"er essentially from that of D. Sedgivicki 

 (see §§ 82, 122). The length of the ossicles is about twice the diameter : thus in a stem 

 with diameter ca. r4 mm., the length is from 2'5 mm. to 3 mm. ; but in El 6027, 

 with a diameter 2 mm., the unusual length of 7*5 mm. is to be seen. 



§ 105. The Median region manifests a rapid increase in width, with a rapid decrease 

 in the height of the ossicles, which grow slightly more swollen, though with thinner 

 walls, and come to alternate regularly {e.g. El 6027) or to break up irregularly {e.g. 

 E 16024, PI. I. fig. 3). 



§ 106. The Proximal region is markedly annulate, but the projecting rings are 



* Tliis is a squeeze from the original of Bakrandk, pi. 27, f. 1. 



