DIPLOGRAPTUS. 



245 



Figs. 165 a — c. — Diplograptus (Ortho 

 graptus) pristis (Hisinger). 



^ ! 



& 



* 





Scotland is somewhat uncertain, but specimens occur in the Upper Glenkiln beds 

 associated with Dicellog. patulosus and Glimacog. antiquus, var. lineatus, which may 

 be referable to it. In the Scottish examples the thecse are not quite so closely set. 



Collections. — Sedgwick Museum, British Museum 

 (Natural History), Lap worth, and the Authors. 



Note. — Orthog. calcaratus and its varieties include 

 the majority of forms which have been hitherto 

 referred by graptolithologists to Diplog. pristis (His.), 

 and Diplog. foliaceus, Murch. Now that these two 

 species are better known, 0. calcaratus appears to 

 us to be sufficiently distinct to be entitled to specific 

 rank. The typical Diplog. pristis of Hisinger has 

 not hitherto been recognised in Britain, but we 

 figure here for comparison examples from the 

 Trinucleus Shales of Wikarbyn, Dalecarlia, Sweden, 

 kindly loaned to us by Dr. Turnquist of Lund, 

 for that purpose. The typical Diplog. foliaceus 

 of Murchison will be found described in the sequel. 



■■■'/ 







i V 

 7 



Complete specimen, natural size, 

 showing form of polypary. Wik- 

 arbyn, Dalecarlia. Coll. Dr. 

 Tornquist. 



Proximal end, obverse aspect as seen 

 in sub-scalariform view ( x 5). 

 Ibid. 



Reverse aspect (?) as seen in sub- 

 scalariform view. Ibid. 



Diplograptus (Orthograptus) rugosus, Emm., var. apiculatus, nov. Plate XXX, 



figs. 7 a — d. 



1880. Diplograptus rugosus, Lapworth, Aim. Mag. Nat. Hist. [5], vol. v, p. 168. 



Polypary biconvex, from 2 — 4 cm. in length, widening gradually from 1 mm. 



till maximum breadth of 3'5 mm. is attained. Sicula conspicuous with 



stout virgella. Thecae twelve to eight in 10 mm., walls approximately 



straight or with slight flowing sigmoid curvature ; overlap one half, 



widening rapidly in direction of apertural margin, which is wide, horizontal, 



approximately straight and mucronate in bi-profile view ; excavation 



very conspicuous. 



Description. — The polypary widens quickly at first but then more gradually, 



so that the maximum breadth is not attained till about 2 cm. from the proximal 



end. The sicula, when seen to its full extent, is 1*5 mm. in length; the virgella 



is conspicuous, and there is a spine on the opposite side of the aperture. Th. I 1 



originates from it at a point about half way along its length, and then grows 



downward until it reaches the level of the aperture, when it curves round, 



growing upward and outward for a short distance, giving off a spine where the 



change in direction of growth takes place ; its aperture is everted and provided 



