ORTHID A. 225 
while the brachial processes are formed of two short prominent lamine. The quadruple 
muscular impressions are arranged in two pairs, and longitudinally divided by a widish 
mesial ridge. 
Length about 5, width 6, depth 2 lines. 
Obs. Mr. Salter has identified this small species with the Bohemian O. redux, and 
I am of opinion that, although the Budleigh-Salterton shell is smaller than the one 
so named by Barrande, the resemblance is sufficiently close to warrant the supposed 
identity. It seems likewise, as stated by Mr. Salter, to bear a resemblance to the shell 
described by M. de Verneuil, in the ‘Bulletin Soc. Géol. de France’ (2nd ser., 
vol. x, p. 993, pl. xxvi, fig. 9, 1855), under the designation of O. festudinaria, Dal. ; 
but in this instance, as in that of Barrande, internal casts alone are figured, so that it 
is hardly possible to feel entirely satisfied with an identification based upon such in- 
complete material. ortunately with us the species is exceedingly abundant, occurring as 
sharply preserved external impressions as well as internal casts of both valves, so that 
by the aid of gutta-percha the perfect interior and exterior of both valves can be re- 
produced. 
Position and Locality. Orthis redue was discovered, for the first time in England, 
as one of the most abundant of the numerous species of fossils that occur in the red 
and whitish sandstone and quartzite pebble-bed at Budleigh-Salterton, in Devonshire ; 
but these pebbles were derived from beds not found ¢m sétw in the locality, and it is still 
impossible to say from whence they have been drifted. Mr. Salter seems to consider the 
age of the rock from which the pebbles were derived to be that of the Lowest Llandeilo 
or the Arenig group, while by some other geologists it has been referred to the Caradoc. 
Orthis redux has also been found by the Rev. P. B. Brodie in erratic boulders, similar 
to those that occur at Budleigh-Salterton, in the Drift near Warwick.! On the Continent 
it is abundant in the quartzites at May, near Caen, in Normandy, where it has been 
known for many years ;? also in the Lower Silurian of Bohemia. 
1 «Geological Magazine,’ vol. ii, p. 566, 1865. 
2 It occurs at May in company with Homalonotus Brongniarti, Conularia undulata, &c. See Deslong- 
champ’s “ Notes pour servir 4 la Géologie du Calvados,” ‘Bulletin de la Soc. Linn. de Normandie,’ vol. viii. 
The quartzite sandstone of May is referred to the Caradoc group. It is this May district to which Mr. 
Salter points as the origin of the Budleigh-Salterton fossiliferous pebbles. 
