486 BRITISH GRAPTOLITES. 



Horizon and Localities. — Llandovery (zones of M. gregarius, M. convolutus, and 

 M. Sedgwiclcii). 



8. Scotland : Dobb's Linn; Belcraig Burn ; Garple Linn ; Sundhope-on -Yarrow. 

 Ireland' : Coalpit Bay, Donaghadee. Wales .- River Twymyn, near Llanbrynmair. 



Associates, etc. — Monog. intermedins is a common fossil in the Upper Birkhill 

 Shales and their equivalents. It occurs in the zone of M. gregarius, associated with 

 M. triangulatus, M. gregarius, Glyptog. tamariscus, etc.; in the M. convolutus zone 

 with M. convolutus, M. lobiferus, M. Clingani, M. limatulus, etc. ; and in the M. 

 Sedgivickii zone with the zone fossil and M. tennis. 



Collections. — Belfast Natural History Museum, Sedgwick Museum, Lapworth, 

 and the Authors. 



VI. B. {(■) : Monograpti in which the thecal are uniform, and the polypary has 



dorsi- ventral curvature. 



Monograptus c/. elongatus, Tornquist. Plate XLIX, figs. 5 a—c. 



1899. Monograptus elongatus, Tornquist, Monog. of Scanian Eastrites Beds, p. 17, pi. iii, figs. 

 12—18. 



Polypary long, irregularly flexed, though usually more or less arcuate, with a 

 very slender thread-like initial portion, widening almost imperceptibly to a 



maximum breadth of 1 mm. Thecas eight or 



Fig. 342.— Monograptus cf. elongatus, llme in 10 mm., of Uniform type throughout, 



Tornquist. , J l & 



elongated sub-triangular, isolate about one- 



V ■ . 



/p third of total length, and with one-half of 



free region involved in the apertural barb. 

 Description. — The polypary is more or less 

 s| arcuate, but often so slender that it appears to be 



A somewhat irregularly flexed. In Britain it has only 



been found in a fragmentary condition. 



The thecas, which are usually on the convex 

 margin, but not invariably so in the irregularly 



Distal thecse, in partial relief. Enlarge- n ^ • ^• • -\ ^ ^ i it n 



ment of part of pi. xlix, fig. 5 a nexed individuals, have a long slender adnate region, 



whose ventral walls show slight concave curvature, 

 and a shorter slender isolate region of which about one-half is involved in the 

 formation of the apertural barb. The appearance of this barb after compression 

 suggests that there may have been some torsion of the thecal axis, but it is possible 

 that with such a slender polypary the appearance is due to the irregular flexure 

 of the whole polypary. 



