242 BRITISH GRAPTOLITES. 



Llanystwmdwy, near Criccietli ; Spittal Road Railway Cutting, Pembrokeshire, etc. 

 Treland: Carnalea, Co. Down ; Coalpit Bay, Co. Down. 



Associate*, etc. — Var. vulgatus seems to be a 



Pig. 160 d. — Orthograptus calcaratus, var. mil- . ' 



jatus, Lapw. MS. very abundant tossil in the Lower riarttell 



Shales of South Scotland, where it occurs 



typically in the zone of Olimacog. Wilsoni, and 



is associated witli Glimacog. bicornis, Orthog. 



ti-)i]i rat us, var. intermedins, and Dicranog. Nichol- 



soni. It ranges up into the zone of Dicranog. 



v. 



Clingani, where it occurs with Orthog. truncatus 

 and var. pauperaius, and a few examples are 

 found in still higher beds. It has not yet 

 been discovered with certainty in the Upper 

 Glenkiln Beds of S. Scotland, but in both N. 

 , _. , . ,. . , .„ and S. Wales it appears to occur at this horizon 



J. Distal thecoe as seen in sub-scalariform L L 



view. Enlargement of part of same speci- associated with D'wranou. brevicaultS, Meson. 

 men as Fig. 160 b. ■' •' 



multidens, and other forms. 

 Collections. — Sedgwick Museum,' Geol. Surveys of England and Scotland, 

 Fearnsides, Lap worth, and the Authors. 



Var. acutus, Lapworth MS. Plate XXX, figs. 3 a — c. 



Another variety, somewhat resembling var. vulgatus in the form of the polypary 

 and in the absence of large basal spines, is especially characteristic of the Glenkiln 



Shales and their equivalents. The polypary widens 



Fig. 161. — Orthograptus calcaratus, var. _ . . 



acutus, Lapw. MS. rapidly from 1 mm. to 4 mm. within 1*5 cm. of the 



proximal end, and the thecae number twelve to nine 

 in 10 mm. instead of ten to eight as in the typical 

 form. They appear to be inclined at a higher angle 

 also, and the apertural margins have a distinct flange 

 and are more incurved and everted in bi-profile view 



Distal thee*, snh-sealariform view. tlian tn0Se ° f either ™r. Vulgatus OV 0. adraratus. 



Enlargement of part of pi. xxx, Horizons and Localities.— Glenkiln Shales ; Di- 



cranograptus Shales. 



8. Scotland : Birnock, Leadhills, etc. 8. Wales : Spittal Road Railway Cutting, 

 near Clarbeston Road ; Drefach, Mydrim ; Dewi Fawr. N. Wales: Conway Cutting. 



Associates, etc. — Var. acutus occurs in the Glenkiln Shales, associated with 

 Dicellog. sextans, 1J. divaricatus, J), intortus, Didymog. swperstes, Cryptog. tricornis, 

 and other forms. It also occurs in the Dicranograptus Shales, associated with 

 Dicellog. sextans, Dicranog. brevicaulis, and Mesog. multidens. 



Collections. — Geological Survevs of England and Scotland, Lapworth, and the 

 Authors. 



