MONOGRAPTUS. 



471 



Affinities. — Monog. urceolus resembles M. proteus somewhat in its general 

 fashion of growth, but has different proximal thecae. From M. decipiens, which 

 it resembles in the general thecal characteristics, it differs in some details of the 

 thecae and in its general plan of growth. 



Horizon and Localities. — Llandovery (zone of M. convolutus). 



S. Scotland: Belcraig Burn ; Duffkinnel, Wamphray. 



Associates, etc. — Monog. urceolus is not a very common fossil in a complete state, 

 but it is possible that many fragments which occur in the zone of M. convolutus 

 should really be referred to it; it is found with M. convolutus, M. Glingani, M. 

 lobiferus, etc. 



Collections. — Geological Survey of Scotland, and Dr. Dairon, Kelvingrove 

 Museum, Glasgow. 



VI. A. (b) : Monog rapti in which the thecae are bi-form and the polypary has dorsal 



curvature. 



Monograptus triangulatus (Harkness). Plate XL VII, figs. 4 a—f. 



1851. Bis) 'rites triangulatus, Harkness, Quart. Jouru. G-eol. Soc, vol. vii, p. 59, pi. i, figs. 3 a — d. 

 1876. Monograptus triangulatus, Lapworth, Geol. Mag. [2], vol. iii, p. 359, pi. xiii, figs. 5 a, b. 



Figs. 327 o — c. — Monograptus triangulatus 

 (Harkness). 



a. Proximal fragment in relief, showing 



sicula. 430 yards S.S.E. of Bryn°- 

 chwith Farmhouse, Pont Envyd, Car- 

 diganshire. Geol. Survey of England 

 and Wales. 



b. Proximal fragment in full relief. En- 



largement of part of PI. XLVII, fig. 

 4 a. 

 f . Distal thecae preserved as a cast, showing- 

 barbed apertural terminations. Same 

 locality as fig. 327 a. 



Polypary variable in length, but usually small, 

 circinate, with sharply recurved proximal 

 portion, widening at first rapidly, and then 

 more gradually till the maximum breadth 

 of 2 mm. is attained. Thecae ten to eight 

 in 10 mm., on the convex margin, in con- 

 tact only, linear-triangulate in form, free 

 four-fifths of length, with small barbed 

 apertural terminations, in which only one- 

 fourth of the thecal length is involved. 

 Description. — The polypary is commonly about 

 3 — 4 cm. in length, but there is one long specimen 

 in the Kelvingrove Museum, Glasgow, that has a 

 length of 10 cm. exclusive of the circinate portion ; 

 such specimens must, however, be rare. 



The sicula is small, measuring aboiit "9 mm. in 

 length, reaching nearly to the level of the top of 

 th. 1, which is appressed to it throughout its 

 extent, and then grows away from it for another 

 •5 mm., terminating in a barbed apertural region. 



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