There cannot be the smallest uncertainty as to the identification of the Spirifera Verneuilii 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 Leptoena 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 Verneuilii 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 evidenceto 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 additional 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 remaining 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 Lesueuri was found by M. Rouault at Guichen, in Brittany, in a white or bluish sandstone, or quartzite, which he refers to the Lower Silurian series, as forming part of his "Etage du Gres Armoricain," referred by Mr. Salter to the age of the Arenig or Skiddaw slates (the lower Llandeilo of Murchison). "When recently in Paris, M. de Verneuil assured me that he and M. Triger had discovered the same shell in the "Gres a Bilobites" of St. Leonard, Sarthe—the rock being situated under the slates of Angers (Lower Llandeilo flags), and Lingula Hawkei (Rouault) and L. Rouaulti 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
