342 



in 1875, to add to our liasic fauna ; and whose general dis- 

 tribution it will be desirable first to consider. The PUcatula 

 Icevigata of d'Orbigny, recorded until now as a French Middle 

 Lias species exclusivelj^, occurs profusely, according to M. 

 DuMOKTiEK, at two placcs, St. Fortunat, and at Giverdy, but is 

 much rarer in other parts of the Ehone district, as at Collonges, 

 Polymieux, and the neighbourhood of St. Bonnet de Cray 

 (Saone et Loire). 



M. A. d'OEBiGNY indicates it at Brulon (Sarthe), and M. E. 

 Deslongchamps, under the name of its synonym, " Harpaz 

 Terquemi," says it is very numerous around and within the 

 little basins of our " recif," (Montabrat) in Normandy. 



Taking this prevalence of the species in north and midland 

 France into account, we would contrast vnth it the fact that it 

 does not seem to be found anywhere else throughout the 

 whole of the continental Lias, — being notably absent from the 

 whole of the Germany Lias ; for on referring to the chief 

 authorities of that country we find that Quenstedt does not 

 name it ; and Oppel mentions that he only met with it once, 

 and then in France, in the Middle Lias of Fontaine Etoupefour 

 (Calvados) : whilst Dr. Bratjns, the latest German writer on the 

 Jura (1871 to 1874) assigns to it no place among the German 

 molluscan fauna. In short, we are led to the conclusion that P. 

 Icevigata is a species which, throughout the Middle Lias of the 

 Rhone, is but sparsely distributed, except at the two points before 

 mentioned, namely ; — at St. Fortunat by the foot of Montout, 

 where it forms an entire bank, and at Giverdy, where it is to be 

 counted by thousands. These with the third locality, namely : — 

 about the Montabart reef (Calvados), give us apparently its local 

 centres ; or to express the case more precisely, we would state 

 that the three places just cited, furnish good data, whence a 

 true zoological centre of distribution may be ultimately deduced. 

 Thence we may fairly infer, the species was naturally transported 

 to our latitude of the great expanse of Jurassic sea, by migration 

 or by currents following the line of coast. The circumstances 

 connected with the finding this new fossil are a little curious. 

 Whilst woi-king at the Middle Lias beds in a quarry at 



