3G2 BRITISH GRAPTOLTTES. 



A. AVith uniform tliecffi — 



1. AVitli curved polypary. 



{(i) Tlio polypary has dorsal curvature. Type Monograptiis cuphiis. 



M. aciiiaces, M. (jreijarlns. 

 [}>) Tlic polypary lias ventral curvature. Type Monograptus hohemicas. 



M. concunnis. 

 (c) The polypary has dorsi-rciUral curvature. Type Monograptus 

 Nilssoni. 



2. With straight polypary. Type Monograptus leptotheca. 



M. regular is, M. jaeiihini, M. variabilis, M. nudus, M. duhius, M. 

 vulgaris, var. ciirtas, M. tuniescens, var. 'minor, M. coinis, M. 

 cP. gotlaiidiens, M. cf. nlttmns. 



B. With hl-forni tliecse — 



1. With curved polypary. 



(a) The polypary has dorsal curvature. Type Moiiograptas revolntns. 

 M. revolutus var. austerus, yixv. prxcarsor, M. diffornds, M. argenten-'<, 

 var. eijgnens, M. limatuhis. 



2. With approximately straight polypary. Type Monograptus colonus. 



M. colonus var. ludensis, var. ronipactus, M. varians, var, pundlus, 

 M. B,oemeri, M. cldmsera, var. Sahvegi, var. semi-spiuosus, M. 

 leintifard.ivensis, var. incipiens. 



I. A. 1. [a) : Monograptl in which the tlieca? are unit'oriD, and the polypary 



has dorsal curvature. 



Monograptus cyphus, Lap worth. I'late XXXVI, figs. 1 a — e. 



187G. Monoyra^itus cijiiJius, Lapworth, Geol. Mag., dec. ii, vol. iii, p. 352, pi. xii, fig.s. 3 a aud 3 c. 



Polypary several cm. in length, slightly arcuate distally with either involute 

 or broadly recurved proximal portion, widening persistently from a long 

 and conspicuous sicula to a maximum diameter of 1*5 mm. Thecas ten to 

 nine in 10 mm., simple tubes with even apertural margins, overlapping one- 

 third of their length near the sicula, and as nnicli as two-thirds in the 

 more mature portions of the polypary. 

 Description. — The form of the polypaiy, with the broad sweeping curve of the 

 early portion, is highly characteristic, but the amount of curvature varies some- 

 what in different individuals, being rather more abrupt in some than in others. 



The sicula alone forms the proximal termination of the polypary ; it is fairly 

 robust and very long, measuring fully 1< nnn. in length ; its apex lies about midAvay 



