Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/559



May 24, 1871.

George Mosley, Esq., 7 St. Paul's Square, York ; Alexander Colvin, Esq., B.A., of Barham Lodge, Weybridge ; Thomas Shepherd Noble, Esq., F.B.A.S., Lendal, York; and Edward Charles Davey, Esq., of Wantage, were elected Fellows of the Society.

The following communications were read : —

1. On the Principal Features of the Stratigraphical Distribution of the British Fossil Lamellibranchiata. By J. Logan Lobley, Esq., F.G.S.

Having been engaged for some years past in investigating the organic contents of British strata, and in the enumeration of the species which have been recorded as occurring in each geological formation, I am enabled to bring before this Society a summary of the stratigraphical distribution of the remains of one of the classes of the Mollusca, the Lamellibranchiata, as far as it is at present known.

The results here presented are submitted with confidence in their reliability as being approximately correct to the present time, since well authenticated species only have been retained in my lists, and extreme care has been taken to exclude those numerous synonyms which are so frequently productive of incorrect conclusions.

The class Lamellibranchiata of De Blainville, or Conchifera of Lamarck, is represented in British strata so abundantly that the genera alone number nearly two hundred. I will not here attempt to give the details of the range and distribution of these very numerous genera, but confine myself at the present time to the consideration of the principal groups of the class.

The classification of the Lamellibranchiata that will be followed is founded on that of Lamarck, and differs little from the one given in the excellent and much used Woodward's ' Manual of the Mollusca.'

In the accompanying Tables the usual geological scale has been adopted. The term Silurian is intended to embrace all the rocks included by Murchison in this " System," namely, from the Lingula Flags to the Passage Beds. Triassic includes the Rhaetic Beds, and Jurassic the Lias and the Oolites.

Table I. (opposite) is intended to show the stratigraphical range as well as the increment, decrement, maximum development, and relative numerical importance of the representation, in our area, of each of the families of the Lamellibranchiata, remains of which occur in the fossiliferous rocks of the British Islands.

In this Table an asterisk standing alone indicates the occurrence of a number of species not exceeding ten, two asterisks indicate the occurrence of more than ten and less than twenty species, three asterisks more than twenty and less than thirty, and so on, each asterisk after the first representing ten species. The number of