110 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoT. 7, 



different latitudes, we find that in each instance the average size of 

 the species is larger in the south than in the north. 



If it might be assumed that the species oi Nerincea reached a 

 larger average size in warm than in cold climates, which is probable 

 from what we know of the recent genera nearest to them in organiza- 

 tion, two conclusions might be drawn from the preceding remarks : 

 1st, That in each of the epochs referred to, there was a similar differ- 

 ence between the climates of the North and South of Europe to that 

 which now distinguishes them ; 2ndly, That in each of the districts 

 mentioned the temperature was gradually falling through the periods 

 of the deposition of the oolitic and cretaceous series of beds. The first 

 conclusion is in itself so probable that it will be readily accepted ; 

 the second must be substantiated by similar results drawn from the 

 comparison of a large series of both animal and vegetable remains 

 before it can be admitted. 



In confirmation, however, of the latter conjecture, we find certain 

 species of Nerincea in the South of Europe in beds of a later period 

 than those in which they are found in the North. Thus N. Brun- 

 trutana, N. grandis (of Voltz, not of Goldfuss), and N. cylindrical 

 which near Lisbon are found in limestones of the subcretaceous pe- 

 riod, occur in France and Germany either in the Portland oolite or 

 the Kimmeridge clay ; and N. nobilis, which occurs in a bed near 

 Lisbon corresponding to our upper chalk, is found at Salzburg in the 

 greensand. But I can find no contrary instance of a species occurring 

 in the South in an older formation than in the North of Europe. 



On some future occasion I shall show that species of other genera 

 of Mollusca which are in the North of Europe confined to the oohtic 

 formations lived on dm'ing the deposition of the cretaceous rocks of 

 Portugal, and I will at the same time explain the grounds on which 

 the classification of the Portuguese beds has been adopted. The 

 facts seem to point out that the seas which covered Portugal during 

 the cretaceous period had a temperature which in the latitude of 

 England only existed during the deposition of the oolites ; and this 

 might be the case if the temperature of these parts of the globe was 

 gradually falling. But I repeat that I am far from thinking these 

 observations sufldcient to prove so important a doctrine, and I only 

 regard them as very shght evidence tending in that direction, and 

 which may be confirmed or contradicted by further inquiries. 



The following species of NerincBa have been found in Portugal : — 



Subgenus 1. Nerin^a. 



N. nobilis, Goldf. 1. 177- f. 9 ; post, t. 12. f. 1 ; common in the upper 



beds of the hippurite limestone near Lisbon. 

 N. Archimedis^, D'Orb. T. Cret. 2. t. 158. f. 3, 4 ; in subcretaceous 



limestone in the cliffs at the Praia de Adrarga near Gintra. 



* Perhaps N. ArcJiimedis may be identical with N. suprajurensis, Voltz and 

 Bronn, Jahrb. 1836, t. 6. f. 2 (not f. 3), and with N. Defrancii, Desh., hut I have, 

 in the doubt, adopted M. D'Orbigny's name, as the Portuguese shell agrees best 

 with his figure. 



