1869. ] DAVIDSON—PEBBLE-BED BRACHIOPODA. 73 
There cannot be the smallest uncertainty as to the identification of 
the Spirifera Verneuilu and Productus above named, although Mr. 
Salter had, in 1863, proposed for the first the designation of Spirifer 
antiquissimus, and for the second that of Leptena Vicaryi; but I 
know that my distinguished friend was willing to admit having been 
misled from supposing the pebbles in question to be of Lower-Silurian 
age, wherein no Productus has ever been detected. Mr. Salter had, 
however, in 1863, hinted at the possibility of some Devonian species 
or pebbles having been introduced into the Budleigh deposit, which 
he alludes to in his description of the so-called Spirifer antiquissimus, 
as well as of the Rhynchonella (R. inaurita, Sandb.) which occurs 
abundantly along with Spirifera Vernewilv in so many of the boulders. 
Unless, therefore, we are disposed to admit that these Devonian species 
did live also in the Lower-Silurian period (which we have no direct evi- 
dence to support), we are unavoidably led to conclude that, with very 
few exceptions, the Brachiopoda found in the Budleigh pebbles are of 
Devonian age, and that the few Silurian ones are the exception, not 
the rule, in the accumulation of boulders in that remarkable locality. 
If we can with certainty determine the age of the last-named © 
species, we shall find considerably more difficulty in dealing with, 
or positively fixing the age of those few species that have been stated 
and supposed to be Silurian. In the memoir by Messrs. Vicary 
and Salter, already quoted, which was published in the 20th 
volume of the ‘Quarterly Journal of the Geological Society, Mr. 
Salter describes and figures nine species of Brachiopoda (the addi- 
tional three being synonyms of the others), and refers them all, 
more or less positively, to the Lower-Silurian period; but, as we 
have already shown, three or four only are Silurian, while the remain- 
ing species are of indubitable Devonian age. 
It is now of much importance to examine with great attention 
those species said to be Silurian; and I admit having experienced 
the utmost difficulty and uncertainty during the progress of this 
investigation, and even now entertain misgivings upon the subject. 
Lingula Lesueurt was found by M. Rouault at Guichen, in Brit- 
tany, in a white or bluish sandstone, or quartzite, which he refers 
to the Lower Silurian series, as forming part of his “‘Etage du 
Grés Armoricain,” referred by Mr. Salter to the age of the Arenig 
or Skiddaw slates (the lower Llandeilo of Murchison), When re- 
cently in Paris, M. de Verneuil assured me that he and M. Triger 
had discovered the same shell in the “Grés 4 Bilobites” of St. 
Léonard, Sarthe—the rock being situated under the slates of Angers 
(Lower Llandeilo flags), and Lingula Hawkei (Rouault) and L. Rou- 
aulti being of a similar age. We have likewise, as one of the most 
abundant fossils of these supposed Silurian pebbles, a small Orthis, 
which Mr. Salter identified with the O. redux of Barrande. I will 
not positively assert that Mr. Salter was mistaken; but a lengthened 
comparison of many of the Budleigh specimens with the two figures 
given by Barrande has led me to think that they may be specifically 
distinct, and that the Budleigh shell is, perhaps, of Devonian age. 
It is true, again, that a small Orthis, somewhat resembling the 
