DICKLLOGRAITUS. 



1 17 



Figs. 90 c and d. — Dicellograptus 

 intortus, Lapw. 



All the thecse resemble those of the OUmacograptus type in having their outer 

 walls approximately straight, but the apertures are intro- 

 verted and the ventral excavations are deeper, wider, and 

 more oblique. 



Affinities. — In general form 1). intortus bears some 

 resemblance to I), caduceus, but the stipes never cross 

 more than once, and often not at all, while the thecas 

 are of a very different type. 



Horizon and Localities. — Glenkiln Shales. 

 Radnorshire : Builth Road (Gwernyfed) ; Wellfield. 

 A\ Wales: Tiddyndicwm. 8. Scotland: Crawick Water ; 

 Dobb's Linn ; Mount Benger Burn ; Glenkiln Burn ; 

 Glencaple Burn, Abington; Rein Gill. Ireland: Carnalea ; 

 Bel voir, Co. Clare. 



Associates, etc. — The typical form of the species is 

 found in the Glenkiln Shales of the Builth district, asso- 

 ciated with Nemag. gracilis., Dicellog. sextans, and other forms. In S. Scotland 

 and Wales it occurs with similar fossils, and in addition with Didynwg. superstes 

 and Olimacog. Scharenuergi. The best specimens are in the collections of Lapworth, 

 Dr. Fraser of Wolverhampton, the Geological Survey of Scotland, and the Sedgwick 

 Museum. 



c. Distal thecae. Enlargement of 



part of PI. XX, fig. 4 d. 



d. Distal view, showing some- 



what different aspect. En- 

 largement of part of PI. XX, 

 fig. if. 



Group III.— T 



Hi' 



1>. 



P 1 



t till,, XII X. 



Dicellograpti, in which the thecas narrow aperturally, have gently curved walls, 

 and slightly introverted apertural portions. 



Dicellograptus patulosus, Lapworth. Plate XXI, figs. 5 a—e. 



1880. Dicellograptus patulosus, Lapworth, Arm. Mag. Nat. Hist. [5], vol. v, p. 102, pi. 5, fig. 18 a — /. 



Stipes several cm. in length, widening very gradually for greater part of their 

 extent, somewhat flexed, diverging at a large angle (320° to 240°). Simla 

 very conspicuous; virgella stout, lateral spines insignificant. Thecas ten to 

 seven in 10 mm., overlapping nearly half their length, free part of outer 

 wall gently curved, narrowing towards aperture. Apertural margin 

 slightly introverted and oblique, opening partly within a narrow triangular 

 excavation, which occupies about one third the width of the stipe. 



Description. — The greatest length attained by the stipes is unknown, but they 

 must have been fully 8 cm. long, and after gradually increasing in breadth from 



