BUDLEIGH-SALTERTON PEBBLE-BED. 345 



In a large quartzite pebble, found at Budleigh Salterton by the Rev. H. Winwood, we 

 find, in addition to the cast of Rhynchonella Winwoodiana ', two internal casts of the 

 ventral valve of an Orthis, which M. de Tromelin at once recognised as the Orthis 

 Hamoni of Rouault. Rouault neither described nor figured his so-termed species. All 

 he has published in reference to it is, " Orthis Hamoni (Rouault) voisin de VO. Michelini 

 et d'une espece propre au Hamilton Groupe de l'etat de New York — Loc. Gahard." 

 M. de Tromelin having seen M. Rouault's type at Rennes alludes to it in his and M. 

 Lebesconte's paper : — " Sur les terrains primaires du Nord du departement de lTlle-et- 

 Vilaine et de quelques autres parties du massif Breton," and adds, p. 617, that the Gres 

 a. Orthis Monnieri is very well developed as far as beyond Caulnes (Cotes du Nord, &c). 



At M. de Tromelin's request Mr. Bayle gave two figures of the exterior and interior of 

 the dorsal valve in the atlas, vol. iv, of the ' Explication de la carte Geologique de Erance.' 

 Erom these last two figures, and the two internal casts obtained at Budleigh- Salterton, 

 we may draw up the following description of the shell : 



By the margin slightly transversely oval, broader than long. Ventral valve very 

 moderately convex, and marked with numerous close, radiating, raised, stria?, crossed 

 at intervals by a few concentric lines of growth. Area narrow. Ventral valve very 

 slightly convex, with a mesial depression commencing at about the middle of the valve 

 and widening as it nears the front. Surface covered with fine, thread-like, radiating 

 striae. In the interior of the dorsal valve the cardinal process is small, so likewise the 

 diverging crural processes. The quadruple muscular impressions occupy an area of 

 about one third of the breadth of the valve and nearly one third of its length, divided 

 longitudinally by a narrow convex ridge. In the interior of the ventral valve the 

 muscular area takes up half the length of the valve and about one third of its breadth. 

 Prof. Bayle's two specimens measured — length 13, width 14, and length 10, breadth 11 

 lines ; the English examples G lines in length by 8 in breadth. The French two specimens 

 are from the Lower Devonian of Nehou (Manche) and Vise, Sarthe. 



M. de Tromelin states in his paper that this species has been several times con- 

 founded with the Orthis Michelini of Leveille, a Carboniferous species, but from which 

 it can be distinguished ; also that it constitutes an excellent horizon whereby to determine 

 the base of the Devonian system in the Departements of the Manche, La Sarthe, Ille-et- 

 Vilaine, the Cotes du Nord, and the Einistere, and in many other places, which will be 

 found enumerated in M. de Tromelin's paper. The same palaeontologist adds that it 

 approaches in character to Orthis Uifelensis. 



18. Orthis Monnieri, Rouault (= 0. Vicargi, Dav.). B. S. Sup., PI. XL, figs. 1 — 8. 



Orthis Monnieri, Renault. Bull. Soc. Geol. de France, 2nd ser., vol. viii, p. 376, 1851. 

 — Vicaryi, Dav. Quart. Journ. Geol. Soc, vol. xxvi, pi. v, figs. 20 — 22, 1869. 



