320 MR. 0. A. SHRTTBSOLE ON TEIASSIC PEBBLES OF [Aug. 1903, 



is not so hard as the Gres de May, and does not seem to have 

 furnished so much of the material of the Budleigh-Salterton pebbles 

 as the latter. Yet it is sometimes difficult to distinguish particular 

 specimens of the two sets of rocks. 



The Gres Armoricain at its base passes into a gres feld- 

 spathique, which to the eye bears a strong resemblance to the 

 quartz-felspar grit both of Budleigh Salterton and the Midlands. 

 Prof. Bonney's remarks on one specimen from the May district 

 will be found farther on (p. 321). 



The fact, first pointed out by J. W. Salter, 1 that the Ordovician 

 fauna of the Gres de May, belonging to the southern or Continental 

 type, is that which is represented in the Budleigh-Salterton pebbles, 

 has never, I believe, been seriously questioned. M. G. de Tromelin, 

 in his monograph on the Gres de May of the Calvados, shows that 

 out of 62 species described, 36 only are common to that locality and 

 to all other parts of the West of France, while 21 of the species 

 are found at Budleigh Salterton. This is a very remarkable fact, 

 when the conditions at Budleigh Salterton are taken into account ; 

 and it shows that the fauna which is characteristic of the Calvados 

 district is largely represented at Budleigh Salterton. Salter was 

 unable to detect any difference in the fossils which are common 

 to the two localities. The bearing of this point is important, 

 because, while Davidson admitted the possibility of the pebbles 

 having come from France, he confessed a preference for a locality 

 as near the present British shore as possible, and thus there has 

 been a tendency to derive the Budleigh-Salterton pebbles from the 

 south-west, whereas the palaeontological evidence alone indicates 

 rather the south-east. 



It may be convenient to reproduce from the monograph of M. G. de 

 Tromelin on the Gres de May 2 the list given by him of the species 

 which are common to the Gres de May and the Budleigh-Salterton 

 Pebble-Bed. This, of course, does not include the Armorican Grit, 

 but it will serve to indicate the probable source from which many 

 of the pebbles have been derived : — 



Dalmanites incerta= Phacops incertus, Ctenodonta bussacensis (Sh.). 



Salter. Ct. erratica, Trom. 



Homalonotus brcvicaudatus (Desl.). Clidcrphorus amygdalus, Salt. 



H. Brongniarti (Desl.). Modiolopsis Heraulti, Trom. 



H. Beslongchampsi, Trom. M. lirata, Salt. 



H. Vicaryi, Salt. ! M. prima (d'Orb.). 



Ribeiria eonformis, Salt. i Lingala Morierei, Trom. 



R. magnified, Salt. \ Orthis budleighensis, Dav. 



Tigillites Bufresnoyi, Rou. (Trachy- ] 0. Berthoisi (var. erratica ?, Dav.). 



derma serrata, Salt.). j 0. exomata, Sharpe. 



Conularia pyramidata, Hceningh. I Vexillum Halli (?) Rou. 

 Area Narcuijoana, Vera. Barr. 



1 Quart. Journ. Geol. Soc. vol. xx (1864) p. 287. 



2 ■ Etude de la Faune du Gres Silurien de May, &c.' Bull. Soc. Linn. Norm. 

 ser. 3, vol. i (1877) p. 74. 



