CARADOCTAN CYSTIDEA FROM GIRVAN. 



391 



§ 125. There is no direct evidence as to the lumen in the median and proximal 

 regions. The indirect evidence of crushing shows that it increased in diameter at least 

 proportionately to the increase in diameter of the stem, and probably much more. 



§ 126. Comparison with Dendrocystis Banandei (see § 107), and D. scotica (see 

 § 149). 



Dendrocystis scotica n. sp. 

 (PI. 11. figs. 10-25. Text-fig. 9.) 



§ 127. Diagnosis. — A Dendrocystis with thecal width nearly 1'5 of thecal height; 

 thecal lobes extending well below stem-attachment ; antibrachial shoulder produced in 

 a distinct process ; plates smooth or some granulate, with greatest diameters from 

 ca. 1"6 mm. to ca. 6*3 mm., the smallest plates being very few. Length of brachiole 

 greater than thecal height; width tapering from 4*9 mm. to ca. "4 ram. Length of 

 stem three times thecal height ; distal region with dimeres abutting to form columnals 

 of slightly dice-box shape ; median region expanding very rapidly, dimeres dichotomis- 

 ing ; proximal region of four columns of wide, hexagonal plates, each with a flange 

 towards its lower margin, and no smaller plates. 



§ 128. Locality. — -Thraive Glen, Girvan. 



§ 129. Horizon. — The Starfish Bed in the Drummuck Group (§ 6). 



§ 130. Material. — All the specimens are in Mrs Gray's collection and bear the 

 numbers G68-G128, Gl30, G131, Gl62, G217-G221, G266. 



G80 is taken as holotype. The rest are paratypes, except GlOO, Gl31, and 

 G219, which are too obscure, and G89 and G266, concerning which, see § 142. 



All are in the form of imprints, and about half retain their counterparts. Scarcely 

 a single specimen, however, can be called complete. 



§ 131. Description. — (Text-fig. 9.) Theca. Outline clearly marked by the outward 

 and downward growth of the lobes, which extend well below the stem-attachment ; the 

 antanal lobe is often more pointed than the other. Narrow end often with almost 

 parallel sides ; concavely truncate, with one angle passing into the brachiole, and the 

 other into a stout antibrachial process (§ 140). 



§ 132. Measurements of Theca in millimetres : — 





Height. 



Width Above. 



Greatest 

 Width. 



Ratio of 



Width to 



Height. 



G80 



G71 



G102 



G90 



G93 



21-3 

 ca. 21 

 ca. 25 

 ca. 26 



35 



15 



ca. 15 

 ca. 15-5 



ca. 31 



31 



35 



ca. 33 



ca. 37 



1-45 

 1-47 



1-4 



1-27 



1-05 



These ratios suggest that the relative height increases with age. If the extension 

 of the lobes below the stem -attachment be taken into account, this tendency is even 

 TRANS. ROY. SOC. EDIN., VOL. XLIX. PART II. (NO. 6). 52 



