Dr. HicliS — Fauna of Ffynnon Beuno Cave, etc. 105 



and this is not of later date than the Neocomian ; and, so far as is 

 known, there are no traces of the curious hooked Splienonchi. But 

 a small smooth spine, originally described by Agassiz under the 

 name of Spinax major,^ is quite commonly discovered both in the 

 Gault, Gi'eensand, and Chalk ; and its remarkable resemblance 

 to the homologous appendage of the Solenhofen Acrodont is very 

 suggestive of its true correlation, in part, with the new species of 

 Acrodus recorded in the foregoing notes. This spine, of course, has 

 already been proved to characterize the Drepanephorus of Egerton ; ^ 

 but it is not in the least unusual for the dorsal fins of distinct genera 

 to be armed with dermal weapons of an essentially similar type. 

 And it is interesting to add, in this connection, that Acrodus levis and 

 Drepanephorus canahcidatus are almost certainly members of the 

 same family of Cestraciontidge, the last-named form having been 

 originally referred in error to the Spinacidee, as is shown by the 

 asterospondylic structure of its vertebral centra.^ 



IV. — The Faunas of the Ffynnon Beuno Caves, and of the 

 Norfolk Forest Bed. 



By Henry Hicks, M.D., F.R.S,, F.G.S. 



PROM Mr. Newton's letter in the February Number of the Geo- 

 logical Magazine, I am inclined to think that he has some- 

 what misunderstood my meaning where I referred to the fauna of 

 the Norfolk Forest Bed in my paper in the December Number. 

 Prof. Hughes had stated in his paper that the bones from the caverns 

 "belong to the newer group of animals found elsewhere in un- 

 doubtedly Post-Glacial river deposits." As Mr. Newton admits 

 " that most of these species have been found in the Pre-Glacial 

 Forest Bed of Norfolk, and it is probable that others of them will 

 yet be found," it is clear that I was correct in my contention that 

 "a very large proportion of the animals occur in the Norfolk Forest 

 Bed." My remarks, however, were not intended to claim the Forest 

 Bed fauna as necessarily of the same age as the remains obtained 

 from the caverns (though on careful analysis they are found to be much 

 more closely allied than is usually supposed), but rather to point out 

 that some highly important questions connected with the compulsory 

 migration of animals in consequence of climatic changes are not 

 taken sufficiently into consideration in these discussions, and also to 

 show the fallacy of any such idea as that species suddenly jumped 

 into existence to mark special stages in Geological history. Surely 

 the species of Northern origin lived where the conditions were 

 suitable for them long before this country was much affected by the 

 gradually advancing glacial conditions, and only arrived here as the 

 increasing severity of the climate compelled them to migrate further 



^ L. Agassiz, " Rech. Poiss. Foss." vol. iii. p. 62, pi. lOb, figs. 8-14. 



2 Sir Philip Egerton, " Figures and Descriptions of British. Organic Remains, 

 Dec. xiii." (Mem. Geol. Surv. 1872), pi. ix. 



3 C. Hasse, " Palaontologische Streifziige im British Museum," Neues Jahrb. 

 1883, pt. ii. p. 66. 



