MONOGRAPTUS. 



873 



Figs. 243 a — c.— Monograptus regularis, 

 Tornquist. 



<\ 



The sicula is small, not exceeding '7 mm. in length, and barely reaches to 

 the level of the apertnre of tli. 1 which arises close to its base. 



The thecK of the proximal portion overlap 

 very slightly and have their apertnral margins 

 approximately perpendicular to the general trend 

 of the polypary ; the overlap, however, increases 

 steadily nntil in the distal portion the thecte over- 

 lap fully two-thirds of their length; they narrow 

 somewhat towards their apertnral margins, which 

 are slightly everted. The length of a mature theca 

 is about 3*5 mm. 



Affinities. — In the general form of the polypary 

 Monog. regularis comes fairly near to M. jaculum., 

 especially as regards the character of the proximal 

 end ; but iu M. jaculum the distal thecae never show 

 so large an amount of overlap. As regards the 

 characters of the distal theca3 M. regularis approaches 

 M. lepUAliec'i and might be confounded with it, but 

 the overlap is never so great, nor are the tliecae so 

 slender as in that species. 



Horizon and Localities. — Llandovery (Birkhiil 

 Shales), zone of M. conuolutus. 



Wales: Rheidol Gorge; River Twymyn, near 

 Llanbrynmair ; Pary's Mt., Anglesea, etc. S. Scot- 

 land : Dobb's Linn ; Belcraig. Ireland : Near 

 Limehill, Pomeroy. 



Associates, etc. — Monog. regnlaris seems to occur most abundantly in the zone 

 of M. conrolntus, associated with M. convolutus, M. involatiis, M. liar^pago, GepUalog. 

 cometa, and other forms. It is possible that it ranges even higher, but this is 

 uncertain. 



Collections. — Sedgwick Museum, Geological Surveys of England and Wales, 

 and Scotland, Jones, Greenly, Fearnsides, and the Authors. 



a. Proximal portion of the polypary, 

 showing' sicnla. East side of old 

 quarry, N.E. of Fagwr-fawr Farm, 

 2 miles E.N.E. of Pont Erwyd, 

 Cardiganshire. Coll. Geol. Survey 

 of England and Wales. 



h. More distal thecffi. Enlargement of 

 part of PI. XXXVII, fig. 3 a. 



c. Distal theciB. Llanystwmdwy, near 

 Criccieth ; Upper Lhxndovery beds. 

 Coll. Fearnsides. 



Monograptus jaculum (Lap worth). Plate XXXVII, figs. 4 a — d. 



1876. Mono(jraptus Hisingeri,\i\x. jaculum, Lapworth, Geol. Mag., dec. ii, vol. iii, p. 851, pi. xii, 

 figs. 2 a—d; and Cat. "West. Scott. Foss., pi. i, fig. 13. 



1877. Monograjjfus Hisingeri, va,r. jaculum, Lapworth, Proc. Belfast Nat. Field Club, p. 130, pi. v, 

 fig. 20. 



1899. Monograpt us jaculum, Tornquist, Lumls Univ. Arsslc, vol. xxxv, pt. 2, no. 1, p. 7, pi. i, figs. 

 15—17. 



Polypary often of great length, straight or with very slight curvature, slender 



