280 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 18, 



in accordance with those of the Continental types, appear to ap- 

 proximate onr Middle Lias more closely to foreign equivalents, than 

 that of any other British section hitherto examined; and this is 

 what we might expect to find at the point where onr English beds 

 approach nearest in distance to foreign shores ; on the other hand, 

 such an approximation in character would lead us to hope that we 

 might here meet with organic forms hitherto supposed peculiar to 

 the Continental Lias. 



3. The Upper Lias. — This division, as defined by Continental 

 geologists, commences with the strata containing Ammonites com- 

 munis, Sow., and terminates with those containing A. jurensis, Ziet. 

 It thus rests upon the zone of A. spinatus, Brug., and is in turn 

 covered by that of A. Murchisonce, Sow. Like the Middle Lias, the 

 Upper Lias of Dorsetshire presents us with two lithological sub- 

 divisions, the lower one argillaceous, the upper one sandy ; but their 

 special characters will be given in the sequel. 



§ II. Descriptions of the Sections. 



1. Blade Ven. — The first section in which the Middle Lias is seen 

 as we proceed eastward from Lyme Regis, and upwards in the order 

 of stratification, is in a cliff called Black Yen, situated between Lyme 

 Regis and Charmouth. Above the beach, nearly opposite the highest 

 part of the hill, there is a succession of cliffs of Lias capped by Green- 

 sand (a, fig. 1). The lower portion of these cliffs, to the height of 

 180 feet, is of a dark slaty-blue colour, and consists of the " Lower 

 Lias Marls" (7); it contains the zones of Ammonites Brookii, Sow. (the 

 local equivalent of A. Turner!, Sow.), A. obtusus, Sow., A. oxynotus, 

 Quenstedt, and A. raricostatus, Ziet., all well defined. Above these 

 beds is a mass of marl, forming a cliff or wall, the dull-grey tint of 

 which strikingly distinguishes it from the darker strata below. This 

 marl, about 90 feet in thickness, is the lower commencement of the 

 Middle Lias, as well as its most westward extension upon this coast. 



On a closer examination we find, however, that the base of the 

 above-mentioned wall (h) is blue and not grey, its real colour being 

 concealed by the crumbling away of the beds above. Nevertheless 

 the Middle Lias, as above defined, commences at the very base, 

 where certain Lower Lias fossils cease and Middle Lias forms appear. 

 This change occurs in some tiers of limestone (?', h) upon which 

 the wall or cliff rests. Between two of these beds of stone, in about 

 eighteen inches of marl, a great number of compressed and metallic 

 specimens of A. raricostatus occur, and this, as far as I know, is the 

 highest limit of that form. The next alternate layer of marl is full 

 of Belemnites ; and here I think the Belemnite-beds may be fairly 

 assumed to commence, and with them the Middle Lias. 



In the 30 feet of blue mail above (Ji), a very elongated Belemnite, 

 B. longissimus, Miller, is the characteristic fossil. This blue marl 

 gives place to some irregular beds of impure semi-indurated lime- 

 stones of a grey colour (</), and these are succeeded by grey marls (/*), 

 becoming shaly in the upper portion. The shales (<?), 6 feet thick, 

 are very full of Belemnites, as is also the thin band of limestone 



