1871,] LOBLEY — BRITISH LAMELLIBRANCHIATA. 411 



Mat 24, 1871. 



George Mosley, Esq., 7 St. Paul's Square, York ; Alexander Col- 

 vin, Esq., B.A., of Barham Lodge, Wey bridge ; Thomas Shepherd 

 Noble, Esq., E.E.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 Peikcipal Feattires of the Sxeatigkaphical Distkibtt- 

 TioN of the British Fossil Loiellibeanchiata. By J. Logak 

 LoBLET, 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 MoUusca, the LameUibranchiata, 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 LameUibranchiata 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 nume- 

 rous genera, but confine myself at the present time to the consi- 

 deration of the piincipal groups of the class. 



The classification of the LameUibranchiata that wiU 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 Mol- 

 lusca.' 



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 Ehsetic 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 LameUibranchiata, remains of which 

 occur in the fossiUferous 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 



