MONOGRAPTUS. 391 



thread, in Avliicli in imperfectly preserved specimens it is almost impossible to 

 detect the long", narrow thecse ; these are nearly in contact, and so delicate for 

 the greater part of tlieir length that it almost aj^pears as if the hooked apertural 

 extremities were isolate from each other at considerable distances. There are 

 commonly five or six thecfe of this proximal type ; those of the more distal 

 portion are simple tubes of the ordinary " cyphus " type. 



Affinities. — In the general characters of the proximal end M. liiRafiilus 

 approaches M. artjentens very closely; it may, however, be readily distinguished 

 by the smooth and even apertural margins of the more distal theoas and the lesser 

 breadth of the polypary throughout the distal portion. 



Horizon and Localities. — Llandovery, Birkhill Shales (zones of M. coni'olutus 

 and M. Sedgwichii). 



S. Scotland: Dobb's Linn, Moffat; Belcraig Burn, Moffat, etc. Lake District: 

 Skelgill. C. Wales: Quarry, N.E. Gwen-ffrwd Uchaf Farm, Pont Erwyd. N. 

 Wales: Pary's Mountain, Anglesea; LlanystwmdAvy, near Criccieth. h-eland : 

 Coalpit Bay, Donaghadee. 



Associates, etc. — M. limatnlus occurs in some abundance in the zones of M. con- 

 voliitns and M. SedgwicJcii; associated with the zone fossil, M. involatus, M. Clingani, 

 M. harpaijo, and Cepitalog. cometa, in the zone of M. convolutus, and with M. tennis, 

 Glgptog. serratiis and 67. seal avis in the zone of M. Sedgwichii ; in the Lake 

 District it occurs with M. argentens in the sub-zone of M. argenteus, and in the Pont 

 Erwyd country with M. leptotlieca at the same horizon. It is only rarely found at 

 any lower horizons. 



Collections. — Geological Survey of England and Wales, Geological Survey of 

 Scotland, Sedgwick Museum, Jones, Fearnsides, Lapworth, and the Authors, etc. 



I. B. 2 : Monogntjdi in which the thoca3 are bi-form and the polyparies are 



approximately straight. 



Monograptus colonus (Barrande). Plate XXXVIII, figs. 8 a — (/. 



1850. GraptcAithus colonus, Barrande, Graptolites de Bolicme, p. 42, pi. ii, figs. 2, 3. 



1852. ? Grajitolithus colonus, Geiuitz, Die Graptolitheu . . . der Grauwackeufonnutiou iu Sachseu, 



p. 38, pi. ii, figs. 33—36. 

 1880. Monogvaptus Rcemeri, Lapwortli, Ami. Mag. ISTat. Hist. [5], vol. v, p. 151, pi. iv, figs. 5 a~ 



he. 

 1883. Monograjifvs colonus, Tullberg, Skaues Graptoliler, pi. i, figs. 22 aud 23. 

 1890. Monograptus colonus, Geiuitz, Die Graptolitlien d. k. niiii. Mus. in Dresden, Mittli. d. k. Min. 



Geol.-Prjilnst. Mus. Dresden, pt. ix, pp. 15, 16, pi. a, fig. 14. 

 1892. Monncjrapius colonus, Barrois, Distribution des Graptolites en France, Ann. Soc. Geol. Nord, 



vol. XX, p. 100. 

 1897. I'ristiixjrajifus colonus, Frecli, Letlia'a Geognostica, vol. i, pt. iii, pp. 655, 656, fig. 209. 



52 



