Botany and Zoology of Devon and Cornwall, 343 



this and the granite, rocks of a sienitic character occasionally 

 occur ; and connected with the same formations we must notice 

 the serpentine, which occupies a limited district on both sides of 

 the Lizard, on the southern coast of Cornwall. Transition 

 limestone is the next formation : it occurs in discontinuous and 

 limited ranges, resting on the primitive, or interstratified with 

 the greywacke schist. This formation, in which polypiferous 

 fossils are of frequent occurrence, is limited to Devonshire ; a 

 small portion of limestone, met with on the northern coast of 

 Cornwall, being, I believe, connected with the more recent for- 

 mations of the opposite coasts of Wales. 



The red sand comes next in order of superposition ; it 

 appears to be referable to two distinct members of the 

 secondary class of rocks, the old and the new red sandstone, 

 (1st and 3d sandstones of Humboldt,) but the limits of each 

 have not, I believe, as yet been very accurately traced. They 

 constitute, on the whole, perhaps the most uniformly fertile 

 portion of the district, forming the cliffs on the southern 

 coast, from beyond Sidmouth to Torbay ; and sweeping round 

 the base of Haldon, comprise what is termed the Clist 

 district, around and beyond Exeter. This rock seldom reaches 

 a greater elevation than from 150 to 200 feet. We may 

 also note, that intervening between this and the former 

 strata, a limited range of amygdaloidal trap occurs. The green 

 sand occupies a tract in the eastern part of Devon, contiguous to 

 Dorset, of which Black-down forms the most conspicuous part ; 

 it is traceable also, with considerable interruption, on the Wood- 

 bury downs, above the Exe on one side, and Haldon Hill on the 

 other, and also on Milburn down, above the Teign, which is the 

 last place in that direction where it occurs. Thin strata of 

 chalk flints are usually found incumbent on the summits of the 

 hills of this formation, which rise to a height of from 800 to 900 

 feet. In point of fertility this can only rank with the poorer 

 portions of the granite. Neither of the two last formations 

 extend into Cornwall, nor do they occupy any of the western or 

 northern parts of Devon, but are limited to the eastern and 

 southern portions of the latter county. There are but few tracts 

 on the whole that can be termed alluvial ; those along the course 

 of the Exe are probably to be ranked amongst the finest and 

 most extensive of the few that do oceur. 



Over this tract, so diversified in its geological character, about 

 780 indigenous species of phaenogamous plants are distributed, 

 about 190 of which, belonging to fifteen natural orders, and 

 forming rather less than one-fourth of the whole, are monocoty- 

 ledonous ; and about 150 belonging to 66 or 67 natural orders, 

 and forming rather more than three-fourths of the whole, are 

 dicotyledonous. I must here premise,' that many genera that 

 have been unphilosophically admitted as indigenous, in some of 

 our British Floras, but whose introduction from a foreign source, 



