BUDLEIGH-SALTERTON PEBBLE-BED. 355 



Nordwestlichen Harzgebirge, pi. iii, fig. 3), a form belonging to the Silurian Spirifer- 

 sandstone. This specimen was kindly lent to me by Mr. Vicary. It occurs in a slightly 

 reddish light grey quartzite pebble, in company with Orthis Budleighensis and a fragment 

 of Trilobite. 



3G. Nuclbospira Vicaryi, Dav. B. S. Sup., PI. XL, figs. 29—31. 



Nucleospira Vicaryi, Dav. Quart. Journ. Geol. Soc, vol. xxvi, p. 79, pi. iv, figs. 15 



—18, 1869. 



Shell transversely suborbicular ; valves very moderately convex, more so near the 

 beaks. In dorsal valve mesial fold wide, of small elevation, rising towards the front. 

 Surface smooth, marked by a few concentric lines of growth. In the interior of dorsal 

 valve the bifid cardinal process projects considerably, while under it rises a narrow ridge, 

 which extends straight to the front, dividing the interior of the valve into two equal 

 portions. The muscular impressions are situated on either side of the posterior half of 

 the ridge. In the interior of the ventral valve a similar mesial longitudinal ridge is also 

 present, which, as in the case of the dorsal valve, divides the valve into two equal parts. 

 Two examples measured respectively — 



Length 7, breadth 9, depth 2 lines. 

 „ 5, ,, 6 lines. 

 Obs. — I described this shell in 1869, and no fresh material seems to have turned up 

 since that period. It seems referable to the genus Nucleospira, Hall ; and approaches by 

 its size and character to N. elegans, Hall ('Pal. New York,' vol. iii, p. 222, pi. xxviii b, 

 figs. 10 and 15). It bears also some resemblance to N. ventricosa, Hall. It varies in 

 shape, some examples being almost circular, while others are more or less transversely 

 oval. JY. Vicaryi is not rare in certain pebbles; no less than thirty-five specimens, 

 representing different ages, having been collected by Mr. Vicary. It is of the age of the 

 " Caradoc " pebbles ; for at Budleigh-Salterton it is associated with an Orthis resembling 

 0. Budleigltensis. In America N. elegans belongs to the Lower-Helderberg Rocks, and 

 an allied form, N. (Spirif.)pisum, Sow., is not rare in our British Upper-Silurian strata. 



37. Orthis Berthoisi, Rouault. Bull. Soc. Geol. de France, 2nd ser., vol. vi, p. 68, 



69, pi. ii, figs. 4 a, b, c, 1848. 



So much discussion and divergence of opinion having taken place and been expressed 

 with respect to this species, that I think it will be desirable to begin by giving a trans- 



