500 



BRITISH GRAPTOLITES. 



Specific Characters of Forms belonging to the Genus Monograptus — continued. 





GROUP IV.-A. 



(UNIFORM)— cantin ued. 



GROUP IV.-B 



. (BIFORM). 



M. 



M. 



M. tarri- 



St. 



M. 



M. 





3{. 







Jcekeli. 



gemmatui. 



culafus. 



discus. 



tortilU. 



SedgwicTci. 



M. Ilalli. 



• MeCoJ/i. 



M. tesiit. 



















var. 

 inornatut. 



Character of polypary 



Long, 



Very 



Coiled 



Very 



Arcuate, 



Straight 



Straighter 



Very 



Coiled 





curved. 



slender. 



in 



small. 



in- 



or 



than M. 



robust 



into plane 





robust 



arciiate, 



conical 



coiled 



curved, 



slightly 



Sedgwicki 



and 



open 







or nearly 



spiral 



into 



fairly 



flexed 





rigid 



spiral 







straight 





disc 



robust 











Maximum width 



3 mm. 



•5 mm. 



1 mm. 



I'omm. 



1'5 mm. 



3 mm. 



3 mm. 



35 mm. 



2 mm. 



Length of sicula 



— 



— 



1'2 mm. 



1 mm. 



— 



1 4 mm. 



— 



— 



— 



Characters of thecte : 





















1. No. in 10 mm. 



9 



6-9 



12 



20—16 



9—10 



10—6 



11—7 



10 



15 



2. Overlap 



2 

 .3 



Insignifi- 

 cant 



i 



— 



\-h 



Slight 



l-i 







— 



3. Apertural region, 



i 



h 



i 



1 



3 



t 



i 



Less retro- 



Like 



No spines ; 



proportion to 







spined 







spined 



verted 



.V. Halli 



otherwise 



width of poly- 















and with 





like those 



pary 















stouter 



spines 



than M. 



Sedgwicki 





of M. 

 Sedgwicki 



4. Proportion of 



h 



— 



— 



— 



_i 



h 



— . 



— 







" hook " to the- 





















cal length 





















Score; Mount Benger Burn, etc. Lal-e District: Spengill. Wales: Bank of 

 Afon Gyffin, Conway. 



Associates, etc. — Monog. (i?,) maximus is fairly abundant in a fragmentary con- 

 dition in some localities following immediately upon the zone of M. Sedgwichi. It 

 sometimes occurs in a more or less well-defined bed at the base of the zone of 

 M. turricidatus, and is commonly associated with M. Halli, M. tarricidatus, M. 

 dextrorsus, M. runcinatas and Petalog. altlssimus. 



Collections. — Sedgwick Museum, Miss M. F. Macphee of Glasgow University, 

 Lap worth, and the Authors. 



Monograptus (Rastrites) equidistans^ (Lap worth). Plate LI, figs. 2 a — e. 



1876. Rastrites distans, Lapworth, Geol. Mag. [2], vol. iii, p. 313, pi. x, figs. 2 a, b. 

 1876. Rastrites distans var. abbreviatus, Lapworth, Geol. Mag. [2], vol. iii, p. 314. 

 1907. Rastrites distans var. abbreviatus, Tornquist, Rastrites and allied species of Monograptus, 

 Lunds Univ. Arsskr., n.s., afd. 2, iii, no. 5, p. 12, pi. ii, figs. 11 — 20. 



' Name modified to avoid confusion with Portlock's species, see ante p. 433. 



