MONOGRAPTUS. 371 



Mill, Long Mountain, etc. /Y. Wa'e^^ : Doeside Slab Quarries, Moel Ferna. 

 Ludlow District : Elton Lane ; Elton-Lndlow Road ; Adferton. 



Associates, etc. — Mo nog. Nilssoiii is a very abundant fossil in the Lower Ludlow 

 Shales, fragments of the distal straight portion, from 5—7 cm. in length, being 

 of frequent occurrence at some localities ; specimens showing the graceful double 

 curvature of the proximal region are much rarer. It usually occurs associated 

 Avitli Monoij. coloiins and var, compactus, M. hoJteiuicus, M. varians and var. 

 pKinllKS, M. Boemerl, M. diit)las, M. niiclnatns var. orhatns, and var. vilcropoma. 



Collections. — Sedgwick Museum, Lapworth, the Authors, etc. 



I. A. 2 : Monograpti in which tho thecje are uniform and the poiypary is 



straight. 



Monograptus leptotheca, Lapworth. Plate XXXVI 1, figs. 2 a — tl. 



1876. MoiVMjraptus lejdotheca, Lapworth, G-eol. Mag., dec. ii, vol. iii, p. 352, pi. xii, %s. -i a -e. 



1876. Monograptihs leptotheca, Lapworth, Cat. West. Scott. Foss., pi. i, fig. 14. 



1877. Monograpius leptotheca, Lapworth, Proc. Belfast Nat Field Club, p. 130, pi. v, fig. 22. 

 1882. Monoijrapfas leptotheca, Tullbeig, Graps. descr. by Hisiager, Bihaug K. Vet. Akad. Haudl., 



vol. vi, p. 12, pi ii, figs. 8 — 12. 

 1899. Monojraptus leptotheca, Tornquist, Mouograptidae of Sjauiau Bastrifes Beds, Lunds Iluiv. 

 Arsslc, vol. XXXV, pt. 2, no. 1, p. 5. 



Poiypary of A^ery great but unknown length, approximately straight and stiff, 



but with slight curvature near proximal end; widening gradually and 



persistently till the maximum breadth of o mm. is attained. Tliecfe eight 



to ten in 10 mm., extremely long slender tubes, overlap considerable 



even in initial portion and reaching a maximum of fully three-quarters of 



the thecal length ; a[)ertural margins even, approximately horizontal. 



Description. — Though the proximal portion is not well known, it is clear that 



the poiypary itself must have been remarkably long, for fragmentary specimens 



exceeding 10 cm. in length are known in which the breadth is uniform throughout, 



while others 8 or 9 cm. in length are also known in which the maximum breadth 



is not attained and in wliicli the thecffi are only about half as long as those of 



the more distal })ortions. In most specimens, indeed, the maximum breadth is 



never seen ; these commonly show a width of about 2 mm. only. 



The mature tliecse have a length of fully 8 nun., their walls tend to show 

 slight curvature, and there is a slight expansion in the apertural region ; so 

 extremely slender are they that on an average a horizontal line in any distal 

 fragment would cut through four or five tlieca3. Their overlap is always con- 

 siderable, and increases throughout the length of the poiypary until the maximum 

 breadth is attained, after which it appears to be constant. 



