158 



BRITISH GRAPTOLITES. 



Eigs. 99 c and d. — Dicellograptus Moffa 

 tensis, Carr. 



c . Proximal theca3. Enlargement of part 



of PI. XXIII, fig. 1 b. 



d. Distal thecse. Enlargement of part 



of counterpart of PL XXIII, fig. 1 b. 



The thecse themselves are 2 mm. in length, and overlap for about half their 

 leno-th; the ventral margins generally show marked convex curvature, but as the 



result of compression may appear much more gently 

 curved. The apertures open wholly inside the 

 general line of the ventral margin of the polypary 

 within conspicuous pouch-like excavations. 



Remarks. — The original figure of Carruthers' 

 type specimen, on which his species D. mojfatensis 

 was founded, is somewhat diagrammatic and shows 

 little but the general form. The specimen which is 

 generally considered as his type occurs on a slab in 

 association with several other examples, and is now 

 in the British Museum of Natural History. It is 

 figured on Plate XXIII, Fig. 1 a. Unfortunately, 

 it is somewhat compressed and distorted, and does 

 not appear to be as representative of the majority 

 of the individuals belonging to the species as are 

 the specimens figured by other authors (loc. cit, supra). Carruthers' type 

 specimen (?) shows the general form of the polypary with the corneous membrane 

 at the proximal end, but it does not exhibit the characteristic abrupt widening 

 of the stipes, nor even their robust nature. Indeed, in these particulars it resembles 

 more closely specimens of D. Morrisi. The specimen figured by Hopkinson 

 (1871) (Plate XXIII, Fig. 1/) is also unfortunately poorly preserved, though it 

 shows the characters of the species fairly well. Perhaps it would be more 

 satisfactory to regard in future Lapworth's specimen, figured Plate XXIII, 

 Fig. 1 b, as the type of this species, as it is well preserved, represents a form 

 closely allied to, if not identical with Carruthers' presumed type, and is character- 

 istically distinct from all other species. 



Affinities. — In its general form D. mojfatensis bears some resemblance to 

 D. Morrisi, but is a more robust species, and the initial axillary angle is smaller. 

 In the characters of the thecas it approaches D. elegans, but differs conspicuously 

 from that species in its mode of growth. 



Horizon and Localities. — Llanvirn (Upper Arenig of Hicks), Lower Llan- 

 deilo (Hicks), Upper Skiddaw Slates, Glenkiln, Lower Hartfell (zone of 

 Climacog. Wilsoni). 



S. Scotland : Dobb's Linn ; Craigmichan Scaurs ; Grlenkiln Burn ; Hartfell ; 

 etc. Lake District : Thornship Beck ; Mosedale Beck ; Barf ; Randal Crag ; 

 Bassenthwaite Sandbeds. Wales : Tiddyndicwm ; Abereiddy Bay ; Llanvirn 

 Quarry ; Llandrindod Wells ; Grwernybrain Dingle, Welshpool. Ireland : Ballygrot. 

 Associates, etc. — D. mojfatensis has a somewhat longer range in time than 

 most of the Diccllograpti. It occurs in the Upper Skiddaw Slates (Llanvirn) 



