lli-i. 



BRITISH GRAPTOLITES. 



Figs. 322 a and b. — Monograptus Clin 

 gani (Carruthers). 







.- ^ * 



* 



I 



twelve to seven in 10 mm., of the general type of those of M. lobiferus, but 



with only one-half to one-third of the thecal length involved in the formation 



of the lobe, which occupies from one-half to two-thirds of the breadth of the 



polypary ; the apertural margin faces obliquely downward and inward. 



Overlap slight. 



Description. — The polypary must have attained several cm. in length ; fragments 



of the proximal portion are, however, of commonest occurrence, and are far more 



easily identifiable than those of the distal portion ; they are all robust. 



The sicula has a length of 1*2 mm. and reaches to the level of the top of th. 1. 



The thecal of the proximal portion do not as a 

 rule exhibit so much retroversion of the apertural 

 region as those of the maturer parts of the polypary, 

 in fact they frequently appear to possess the hook 

 characteristic of the group of M. priodon rather than 

 the lobe of the group of M. lobiferus. Distally, 

 however, the amount of retroversion increases till 

 the thecal angle exceeds 180°, and the lobate 

 character is more definite, though it is always less 

 pronounced than in the more typical members of the 

 group. In this respect the mature thecas show a 

 decided resemblance to those of M. communis (group 

 of M. convolutus), though in the latter case the 



«. Proximal portion, showing sicula. , . , , . -. ■ „ rm .■■ 



Duffkmnei, near Moffat ; Birkhiii lobate character is less significant, lnetnecae appear 

 6. Dfsta^thec^sonSat^'ompressed. to have diminished somewhat rapidly in breadth in 



Co°ii b EUer ;Uppei ' Bil ' khillShak ' S ' their apertural regions, which exhibit an amount 



of torsion sufficient to cause all the actual aper- 

 tural margins to face in one direction, either towards, or away from, the 

 observer. Thus after compression there is frequently seen a view in which the 

 adnate regions of the thecas are very conspicuous, while the isolated apertural 

 regions are visible merely as a fringe of hooks, or even completely embedded in 

 the rock. 



Affinities. — In respect of the shape of the polypary Monog. Olihgani approaches 

 both M. millcpeda and M. communis, from either of which species it may be readily 

 distinguished by its far more robust proximal portion. As respects the distal 

 theca? Monog. Cling ani resembles M. communis more closely than any other form, but 

 may be distinguished by the thecse being larger and having a greater fraction of 

 the thecal length involved in the lobe, which also shows a greater amount of retro- 

 version. 



Horizon and Localities. — Llandovery (zone of M. convolutus, especially M. 

 Clingani band). 



8. Scotland: Dobb's Linn; Belcraig Burn; Moory Syke; Whitehope Burn, 





