146 BRITISH GRAPTOLITES. 



Shropshire: Spy Burn. S. Scotland: Birnock Water; Meggat Water, etc. 

 Wales : Llandrindod Quarry, Builtli ? 



Associates. — Var. salopiensis occurs in Shropshire usually associated with 

 Nemag. gracilis, Leptog. latus and Dicranog. brevicaulis. It has also been found in 

 S. Scotland associated with the typical Glenkiln species. Good specimens are in 

 the collections of Lap worth, the Sedgwick Museum, and the Geological Survey 

 of England. 



Dicellograptus intortus, Lapworth. Plate XX, figs. 4 a—f. 



1880. Dicellograptus intortus, Lapworth, Ann. Mag. Nat. Hist. [5], vol. v, p. 161, pi. 5, fig. 19 a. 

 1902. P Dicellograptus affinis, T. S. Hall, Geol. Survey, N.S. Wales, vol. vii, pt. 2, p. 50, pi. xii, fig. 2 ; 

 pi. xiii, fig. 2. 



Stipes 4 cm. or more in length, gently curved or crossing, diverging at an 

 angle of 340° or more ; axillary angle therefore very small. Sicula rarely 

 seen. Virgella and lateral spines conspicuous. Thecse fourteen to eleven 

 in 10 mm., free outer wall approximately straight, overlapping for one 

 half to one third of their length of 1*5 mm. Apertures slightly introverted, 

 ventral excavation wide, deep, oblique, and roughly triangular in form, 

 occupying about half the width of the stipe. 

 Description. — The stipes diverge from each other at a large angle, and hence 

 the axillary angle is characteristically small, smaller indeed than in any other 

 Dicellograptus except D. anceps. The angle of divergence appears to be approxi- 

 mately constant in young forms ; but in fully developed specimens, after 10 or 15 

 niiii., the stipes show gentle convex curvature of their ventral margins and 

 grow upward, with their stipes approximately parallel to each other, or else 

 cross each other at a point 2 — 3 cm. vertically above the initial region. The 

 stipes widen gradually from "5 mm. at their origin to 1 



Figs. 90 a and 1. — Dicellograptus , ,., 



intortus, Lapw. mm. m breadth. 



The sicula exceeds 1 mm. in length when perfect, 

 but is frequently broken at the apex, and is concealed 

 for the greater part of its length by the earliest formed 

 thecse. Its apertural spine, however, can usually be 

 detected. The proximal thecae originate basally and 

 a. Obverse view. Enlargement of grow horizontally for the greater part of their length, 

 /. i;!'v'!se f vie^ X showini' apex thereby giving to the axil the appearance noted in 

 FigS: ° n Same Slab as Dicellog. anceps. In well preserved specimens a short 

 stout spine is seen to be given off from each of the 

 two proximal thecae at the point where they bend round to grow upward, and 

 similar spinus may also be detected on other thecae near the proximal extremity. 



