MONOGRAPTUS. 459 



Horizon and Localities, — Wenlock Shales (zone of M. riccartonensis) . 



S. Scofia ml: Milk Water ; Hyndlee Burn, etc. Wales : Newbridge-on-Wye ; 

 River Wye, near Builth Bridge; behind drove Cottages, Rhayader Road, near 

 Builth, etc. Shropshire: Walcot Quarry, Chirbury. Lake District: Rawthey 

 Bridge. 



Associates, etc. — Monog. capillaceus is a fairly abundant fossil in the Lower 

 Wenlock Shales, where it occurs in the zone of M. riccartonensis, associated with 

 M. riccartonensis and M. priodon. 



Collections. — Geological Survey of Scotland, Watney and Welch, the Authors. 



Monograptus retroflexus, Tullberg. Plate XLVT, figs. 5 a — c. 

 1882. Monograpt-us retroflexus, Tullberg, Skanes Grapt,, p. 25, pi. i, figs. 18—20. 



Polvpary slender, arcuate, with abruptly reflexed proximal portion, widening 

 very rapidly in the initial region and having an average uniform breadth 



(after the first few mm.) of "75 mm. Thecse 



Fig. 317.— Monograptus retroflexus, ten j n jq mm usua H y on \\\e COUCave margin 



Tullberg J ° 



except near proximal end ; slender tubes with 

 insignificant overlap, of the general type of 

 those of M. lobiferus, with the apertural 

 region bent back completely upon itself, but 

 with a very small fraction of the thecal length 

 involved in the lobe, which is relatively con- 

 spicuous, occupying from one-half to one- 

 third of the total breadth of the polypary. 

 Description. — Fragments only of this species are 



Distal tlieca;. Same locality as PI. i • tj '±. • -u j. 1 1 cc • j.1 l 



XL vi, figs. 5 a— c. known m Britain, but they are sufficiently charac- 



teristic to render the identification certain. 



The thecae are usually well seen, and their ventral walls show decided 

 curvature. 



Affinities. — The general form of the polypary and the characters of the thecse 

 approximate perhaps more closely to those of M. capillaceus than to those of any 

 other graptolite, but the species may be distinguished by its more rapid widening 

 and more slender average width, whilst the thecal lobe is more tightly coiled. 



Horizon and Localities. — Wenlock Shales (zone of Cyrlog. rigidus). 



Welsh Borderland : Quarry near Nant Prophwyd, Builth Road; Dulas Brook, 

 Builth Road ; Kings wood, S.W. of Long Mountain. 



Associates, etc. — Monog. retroflexus is a somewhat rare fossil in the Upper 

 Wenlock Shales, occurring, so far as our knowledge goes, exclusively in the zone of 



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