148 NEOZOIC TIME. [CHAP. IX. 



the inference that the mixture of sea and salt-lake water 

 was not at first favourable to molluscan life ; the assem- 

 blage of species is a small one, and consists almost entirely 

 of bivalves, their shells having that dwarfed appearance 

 which is generally the case with those living in unfavour- 

 able habitats. No Cephalopoda, Gasteropoda, Brachiopoda, 

 Echinoderms, or Corals occur, but all these come in with 

 the Lower Lias, proving that the waters were at first 

 shallow and unfit to support these creatures, but that 

 further submergence opened up free communication with 

 the outside sea, bringing in a greater depth of water, and 

 all the conditions favourable to the increase of molluscan 

 life. The Liassic sea, indeed, with its large and active 

 reptiles, its numerous fishes, and other inhabitants, must 

 have presented a great contrast to the heavy and nearly 

 lifeless waters of the salt Triassic lakes. 



The plants and insects of the Rhsetic and Lias also testify 

 to the alteration of the climate, the humidity of the air, 

 and the general fertility of the surrounding region. It is 

 remarkable, however, that the insects are chiefly of a 

 small size, and not such as might be expected to occur in 

 association with the semi-tropical assemblage of marine 

 creatures, but are rather such as would inhabit temperate 

 climes at the present day. On this point Sir A. Ramsay 

 has some interesting remarks. During the Triassic and 

 Liassic periods, he says, it is not improbable to suppose 

 that the mountains of Wales were at least double their 

 present height, and were, therefore, 5,000 to 6,000 feet 

 high, so that if a tropical or warm temperate fauna existed 

 along the coast, a cold temperate land-fauna might exist 

 among the hills. Now Professor Edward Forbes, while 

 dredging along the coast of Lycia (Asia Minor), " observed 

 that during the rainy season, the surface of the water was 

 often partially covered with quantities of dead insects, 

 washed into the sea from the neighbouring land. By far 



