454 BRITISH GRAPTOLITES. 



The sicula is small, about '9 mm. in length, with th. 1 arising- about one-third 

 of the distance along its length. 



The lobes are by far the most conspicuous portion of the theca?, and in poorly 

 preserved specimens are all that can be seen of the thecas. 



Affinities. — Monog. exignus closely resembles M. nodifer when the latter is 

 poorly preserved; for though the polypary in M. nodifer is commonly rather stiffer, 

 the curvature less, and the increase in breadth more persistent, so that distal 

 fragments are wider than any portions of M. exiguus, these are not matters 

 readily discernible in poorly preserved specimens. The same difficulty applies to the 

 thecae. When preserved in full relief the thecse of the two species are obviously 

 distinct, those of M. nodifer having a more conspicuous adnate region, while there 

 is a far greater degree of retroversion and torsion of the apertural region, so that 

 the termination of the apertural region is turned upon itself once more. There 

 may be something of the same kind in a few of the most distal thecas of 

 .1/. exiguus, but it is far less conspicuous than in M. nodifer, and in many 

 cases it would seem to be impossible to detect it at all. In poorly preserved 

 specimens the thecas appear to resemble each other very closely, and there is little 

 to distinguish the two species beyond the more conspicuous and persistent widening 

 of the polypary of M. nodifer compared with the general uniformity in breadth of 

 that of ilf. exiguus. 



From all other Monograpti the form of the polypary in M. exiguus and the lobed 

 nature of the thecse are sufficient to distinguish it. 



Horizon and Localities. — Gala-Tarannon Beds (zones of M. turriculatus [upper 

 part only] and M. crispus). 



8. Scotland: Caddonfoot ; Meigle Quarry; Glendearg ; Grieston Burn; 

 Douglas, near Tushielaw r , etc. Wales: Tarannon River, etc; Llanystwmdwy, near 

 Criccieth ; Forge Corner, Conway. Ireland: Portaferry ; Tieveshilly. Lake 

 District: Great Rundle Beck ; Faith's Gill, Sedbergh ; Browgill, etc. 



Associates, etc. — Monog. exiguus occurs in profusion in beds of Gala-Tarannon 

 age, especially in the zone of M. crispus, where it is commonly associated with 

 M. crispus, M. discus, and M. Marri ; it also occurs, but less abundantly, in the 

 upper parts of the lower zone of M. turriculatus associated with M. turriculatus, M. 

 runcinatus, M. nudus, Rastrites Linnsei, etc. 



Collections. — Sedgwick Museum, Geological Survey of Scotland, Belfast Natural 

 Histoiy Museum, F. G. Black of Cambridge, Lapworth, and the Authors. 



Monograptus nodifer, Tornquist. Plate XLVI, figs. 2 a — </. 



1881. Monograptus nodifer, Tornquist, N;°igia Grapt. Dalarne, ]>. 436, pi. xvii, figs. 2 a— c. 



1882. Monograptus nodifer, Tullberg, Skaues Grapt., vol. ii, p. 25, pi. ii, figs. 30 — 32. 

 1892. Monogra/'tus nodifer, Tornquist, Siljansomrad. Grapt., ii, p. 26, pi. ii, figs. 23 — 28. 



