4§"^ of the Limestone of South Devon. 225 



distinct testacea, that he suggested the South Devon limestones 

 would prove to be of an age intermediate between the carboniferous 

 and Silurian systems, and consequently of that of the old red sand- 

 stone. In alluding to Professor Sedgwick and Mr. Murchison's 

 adoption of the suggestion in 1839, and their bold application of it 

 to all the older sedimentary rocks of Devon and Cornwall, the au- 

 thor states, that the fullest testimony is borne in the papers, con- 

 taining their present views of the structure of those counties, of the 

 source whence the suggestion was derived. 



Appended to the notice was a list of fossils, necessarily very in- 

 complete, from the limited nature of the materials at the author's 

 command. It consisted of sixty-three species ; twelve considered 

 common to the Carboniferous and Devonian limestones, forty-two 

 peculiar to the Devonian strata ; and nine, seven of which are corals, 

 common to the Devonian and Silurian formations ; doubts were, 

 however, entertained respecting the identification of the two species 

 of shells. The author then observes, — should it be uro-ed that it 

 was unjustifiable to assume, from organic remains alone, the age of 

 the Devonshire limestone, it may be replied, that in a district of 

 which little in 1837 was positively known, which is cut off by the 

 granite of Dartmoor from the only base line of the country, the 

 culm measures of central Devon, proved in 1836 by Prof. Sed"-wick 

 and Mr. Murchison to be the representative of the true coal mea- 

 sures, organic remains were the only test by which the age of strata 

 so situated could be determined ; and in support of his aro-ument, 

 he advanced the recent establishment in Cutch and the Desert to 

 the east of it, from the examination of suites of fossils brought to 

 England by Capt. Smee and Capt. Grant, and others procured by 

 Colonel Pottingcr at the request of Colonel S}'kes, of a series of beds 

 unquestionably of the age of the oolites of England, the fossils 

 agreeing in their general characters with those of that geolo^^ical 

 epoch in this country, and being in many instances specifically undi- 

 stinguishable. In this case, mineral characters and order of superpo- 

 sition would have been valueless guides, for the rocks are totally differ- 

 ent in character from those of the same age in England ; and there 

 was no predetermined series of beds from which an order of super- 

 position could be derived. Another instance was noticed of the value 

 of organic remains, if rightly applied, in determining the relative 

 age of a distant region, and in this case of one inaccessible to 

 Europeans, in the Ammonites ol)tained from the Tartar side of the 

 Himalayan mountains. These fossils prove the existence in that 

 unexplored country, of rocks of the secondary epoch, by possessino- 

 that peculiar character in the sutures, which is not found in Am- 

 monites of any other epoch ; they are moreover accompanied by Be- 

 lemnites. 



In advocating the value of fossils, the author, however, be"-s it 

 may be clearly understood, that he would not expunge from the 

 geologist's consideration, the aid to be derived from order of super- 

 position, and under a right control, from the use of mineral compo- 

 sition and litliological structure ; and he would advise the observer 

 Phil. MiKj. S. 3. Vol. 18, No. lie. il/wrcA 1841. Q 



