Geological Society. 513 



posit, or from patches of Falun of more ancient date than others : 

 he also suspected, that where the tropical forms abounded, there 

 would be found a smaller proportion of recent shells. He is, how- 

 ever, now convinced that all the shells belong to one group, or that 

 the forty-four crag species were really contemporaneous in Touraine 

 with the large cones, Cyprseas, Fasciolarias, and other tropical forms 

 of Testacea. At Bossee, where he found these large univalves, as well 

 as the Astrsea, Lunulites, and Dendrophyllia, most fully developed, he 

 obtained the greatest proportion of recent shells, or thirty-two per 

 cent., the average being twenty-five. In making the examinations 

 upon which these results depend, Mr. Lyell states that he always 

 had recourse to the assistance of Mr. G. Sowerby, and in doubtful 

 cases to that of Mr. E. Forbes, or some other conchologist ; and that 

 he excluded from his calculations a great many species of which he 

 did not possess perfect specimens, or a sufficient number to enable 

 the specific identification to be confidently proved. Of the corals 

 collected by the author, forty-three species have been determined by 

 Mr. Lonsdale, only seven of which, or fifteen per cent., agree spe- 

 cifically with those found in the Suffolk crag. This per-centage in 

 the Polyparia is almost exactly the same as that which has been ob- 

 tained from a comparison of the Testacea. Some of the genera of 

 corals, fossil in Touraine, as the Astrsea, Lunulites, and Dendrophyllia, 

 have not been found in European seas north of the Mediterranean; ne- 

 vertheless thePolyparia of the Faluns do not indicate a climate warmer 

 than that which now prevails on the southern coasts of Europe. 



The next general question considered by Mr. Lyell is, whether 

 the Faluns of the Loire and the English crag can be referred to the 

 same geological period, eighty-five per cent, both of the corals and 

 the shells being of distinct species. " Can," he says, " such a con- 

 clusion be embraced on the ground of the corresponding degree of 

 analogy which both deposits bear to the existing fauna, and to the 

 extremely wide departure which both the crag and the Faluns make 

 from the fossils of the Eocene period ? " 



When Mr. Lyell compared in 1839, with the assistance of Mr. 

 Searles Wood and Mr. G. Sowerby, the Suffolk crag shells in Mr. 

 Wood's cabinet, the proportion of recent species in the red crag was 

 found to be about thirty per cent., and in the older or coralline about 

 twenty, or, including both, twenty-five per cent., the same amount 

 as in the Faluns of Touraine ; the analogy of the recent crag-shells 

 being almost entirely to shells of the British seas, and that of those 

 of the Faluns mostly to Mediterranean species. The argument which 

 might be derived in favour of the more modern origin of the crag, from 

 the recent species being precisely those of the neighbouring seas, 

 while the existing species of the Faluns are not to the same extent, 

 Mr. Lyell combats by stating that the whole assemblage of English 

 crag genera and species departs very widely from that of the ad- 

 jacent seas, consisting of northern and southern forms. Thus the 

 Glycimeris, Cyprina and Astarte are northern genera, and of the 

 Astarte there are about fourteen species ; and of genera now known 

 as existing only in equatorial latitudes, are Pyrula, Lingula, and some 



Ann. | Mag. N. Hist. Vol. viii. Suppl. 2 L 



