470 



BRITISH GRAPTOLITES. 



Horizon and Localities. — Llandovery (zone of M. concolutus). 



8. Scotland: Belcraig Burn ; Dobb's Linn ; Clanyard Bay, Port Logan. Lake 

 District: Tributary of Hall Gill. Wales: River Twymyn, near Llanbrynmair ; B. 

 side quarry, N.B. of Fagwr-fawr Farm, Pont Erwyd. 



Associates, etc. — Monog. decipiens is not a very common fossil, but it occurs 

 sometimes in fair abundance, as, for example, at Belcraig, in the zone of M. con- 

 volutu*, where it is associated with 71/. convolutus, M. limatulus, M. Clingani, and 

 M. lobiferus. 



Collections. — Geological Survey of England and Wales, and of Scotland, 

 Sedgwick Museum, and the Authors. 



Monograptus urceolus, Richter. Plate XLVIII, figs. 1 a — d. 



1853. Monograptus urceolus, Richter, Thiirmgische Graptolithen, Zeitschr. d. deutseh. geol. Gesell., 



vol. v, p. 462, pi. 12, figs. 29, 30. 

 1899. Raslrites urceolus, Eisel, Die Zouenfolge <1. ostthuring. u. vogtliind. Graptolithenschiefer, 



p. 6. 

 1907. Monograptus cfr. urceolus, Tornquist, Ristrites and allied species of Monograptus, Lund. 



Univ. Arsskf., n.s., aid. 2, iii, no. 5, p. 18, pi. iii, figs. 5 — 10. 

 1911. Demirastrites urceolus, Eisel, Ueber zonenweise Entwick. d. Rastriteu u. Demirastriten i. d. 



mittelsil. Graptolitheiiscliiefern Thuringens u. Sachsens, p. 15, pi. ii, figs. 25 — 32. 



Figs. 326 a and 6. — Monograptus 

 urceolus, Richter. 





SLS 





Polypary in the form of a loose helicoid spiral, very slender in the proximal 

 portion, but widening rapidly to a maximum breadth of about 2 mm. Theca? 

 eleven to twelve in 10 mm., of two types; those of the proximal portion 



linear and isolate like those of East rites, those 



of the distal portion in contact, broadly 



triangular, with fully two-thirds of the thecal 



length isolate. 



Description. — The loose helicoid spiral starts to 



grow somewhat in the same way as M. proteus, but 



the whole form is very irregular and difficult to 



determine from our British specimens. 



The sicula is small, rather shorter than the 

 isolate part of th. 1. 



The thecas are usually borne on the convex 



margin, but this is not invariably the case. There 



is a comparatively long proximal portion in which 



men on same slab as pi. xlviii, the theca? are of the isolate Bastrites type, but those 



figs. 1 b and 1 c. . 



of the remaining portion are bluntly triangular, 

 with a loose barb at the termination, in which the merest fraction of the thecal 

 length is involved. 



^- 



a. Proximal fragments, showing char- 



acter of proximal thee*. Enlarge- 

 ment of part of PL XLVIII, fig. 1 a. 



b. Distal thecse. Enlargement of speci 



