I 



II 



27 



34-0 mm 



20 



25-0 „ 



8 



11-5 „ 



12 ORDOVICIAN AND SILURIAN BELLEROPHONTACEA. 



Dimensions. — 



Height of shell .... 



Height of whorl at mouth 



Diameter at umbilicus ... 

 Uemarhs. — Shells of this type have been usually ascribed to 8. hilohafiis, but 

 their more compressed shape, narrower dorsum, more rapid increase in the height 

 of the outer whorl, lower position of the umbilicus and semi-oval or semi-elliptical 

 cross-section of the whorls, distinguish them. S. soivcrhyi, Perner, is more closely 

 allied, but it has not the internal transverse thickenings. My ;S'. criipticus from 

 Haverfordwest is closely allied, l)ut differs in the ornamentation and shape of the 

 apertural lobes. We may also compare the American species S. suhcomirressus 

 (Ulr. and Scof.)^ and S. concinnus (Ulr. and Scof.).~ The co- types are in the 

 Sedffwick Museum. 



*i=) 



9. Sinuites pusgillensis, sp. nov. Plate II, figs. 9 — 12. 



Specific Characters. — Shell rounded ; outer whorl wider than high, rapidly 

 increasing in size, especially in width, and completely embracing inner whorls ; 

 dorsum of proximal part narrowly rounded, strongly arched, beconiiug broader, 

 lower and less arched towards mouth. Umbilicus small, deep, situated at 

 rather more than one-third the height of shell ; umbilical slopes small, steeply 

 bevelled, with distinctly marked umbilical edge. Mouth transverse, nearly twice 

 as wide as high, with very shallow broad emargination in upper lip and short 

 broad, rounded lateral lobes. Internal thickenings absent. External ornament 

 unknown. 



Dimensions. — s.m. iig. 



Height of shell . . . 24-5 

 Height of umbilicus . . 90 



Horizon. — Lower Ordovician : Corona Beds. 



Localitij. — Pusgill, near Dufton, Cumberland. 



Remarks. — All the specimens are internal casts. The tyne is iu the Sedgwick 

 Museum, and the paratypes in the British Museum. The outer whorl expands 

 more rapidly in width than it does in 8. soncUeyeiisis, and its narrowly arched 

 dorsum becomes lower and broader towards the mouth. The umbilicus also is 

 situated below the centre of the shell, and there are no internal thickenings. In 

 the shape of the shell and the general characters of mouth, sinus and lateral lobes, 

 ;S^. cancellatus (Hall),^ from the Black River and Trenton groups, appears to be 

 closely similar. 



1 Ulricli and Scofield, ojx cit., p. 873, pi. Ixiii, figs. 40 — 44. 



2 Ihid., p. 874, pi. Ixiii, figs. 36—39. 



3 Ibid., p. 872, pi. Ixiii, figs. 1—14. 



[G. 220(36.] 



[G. 22064.] 



22-0 . 



14-0 mm 



7-0 . 



5-0 „ 



