466 BRITISH GRAPTOLITEN. 



M. Glingani. From AT. lobiferus it differs in the strongly recurved proximal end 

 and in the characters of the theca?, the lobe being relatively less conspicuous and 

 involving a smaller fraction of the total thecal length. From M. Glingani, with 

 which it agrees in the curvature of the proximal portion, it differs conspicuously 

 in the characters of the thec;e in that portion. There is more resemblance in the 

 theca? of the distal portions, though those of M. millepeda are set at a higher angle, 

 giving rise to a different appearance, especially after compression. 



Horizon and Localities. — Llandovery (zone of M. gregarius, sub-zone Af. 

 argenteus). 



8. Scotland: Dobb's [jinn ; Lockerbie, etc. Wales: Parys Mountain, Anglesea ; 

 Rheidol Gorge, 440 yards S.S.F. Bryn-chwith. Lake District : Skelgill. 



Associates, etc. — Monog. millepeda occurs at the top of the zone of M. gregarius 

 in the M. argenteus suit-zone, where it is found with M. gregarius, M. leptotheca, 

 M. triangularis, Glyptog. tamariscus, Glimacog. Hughesii, Petalog. minor, etc. 



Collections. — Geological Survey of England and Wales, British Museum (Natural 

 History), Jones, Fearnsides, Sedgwick Museum, Lapwortli, and the Authors. 



Group VI. 



Monograpti in which the mature theca? are triangular or conical in form with 

 reflexed apertural margins. 



In the Monograpti included in this group the tendency of the theca? to 

 'isolation is much more completely carried out than in any of the groups already 

 described, while at the same time the tendency to lobatiori is less, being rela- 

 tively insignificant. 



Thecal of two types are of fairly common occurrence, those of the proximal 

 portion of the polypary showing a tendency to a still greater degree of isolation than 

 those of the maturer portion. Sometimes, indeed, the isolation is so conspicuous as to 

 approach that characteristic of the members of the group next to be described 

 (Bast rites). Thus there are forms like M. convolutas and M. triangulatus, in which 

 the proximal theca? appear to be completely isolate linear tubes with only the merest 

 fraction of their apertural extremities reflexed. This reflexed part is so short as to 

 constitute a distinct " barb " rather than a " lobe " ; and may be open (M. urceolus) 

 or more or less completely closed (Af. triangulatus). 



The distal theca?, when flattened, are, as a rule, more or less broadly triangular 

 in form, with usually only a small fraction included in the formation of the 

 terminal apertural barb. \\\ general, fully three-fourths to seven-eighths of the 

 upper wall of the theca is free, and of this free portion only a fraction ranging from 

 one-fifth to one-third is involved in the barb. 



Some forms, indeed, like M. communis, in which one-third of the total thecal 



