Vol. 50.] OSSIFEROUS FISSURES NEAR IGHTHAM. 185 



Y. Conclusions. 



It is a little difficult to sum up the questions raised by the 

 Ightham fissures and their contents until one has read Mr. ]S T ewton*s 

 paper. Still I think there are certain points which must be 

 settled before a correct estimate can be made of the palaeontological 

 significance of these discoveries. They appear to me to be these : — 



1 . Was the filling up of the fissures effected by (a) a marine 

 submergence, or even (6) were the contents washed in from a land- 

 surface above? or 



2. Were the fissures filled by the action of a river from the side ? 



3. Was the opening of the fissures a continuous and recurring 

 one, after the first introduction of fissure-material, and the hereto- 

 fore recognized Pleistocene mammalia ; thus making the contents 

 of the fissure belong to any age since the first opening ? or 



4. Did the river, when it first entered the fissures, find them of 

 practically the same width as now ? Was the filling confined to 

 one period, and therefore the fossils all of one geological age ? 



The answers that suggest themselves to me are the following : — 

 1. (a) The fact that we have raised beaches extending a long 

 way inland, left as relics of submergence, suggests that, had such an 

 action taken place in the Ightham neighbourhood, with its land- 

 locked depressions, some vestiges of it at least would have been 

 left ; and of all things in the world no traps would have been more 

 fitted for the purpose than empty fissures. Yet I must admit 

 that I have been unable to find a single particle of an obviously 

 marine deposit. On the other hand, the whole of the contents are 

 of terrestrial origin ; and this, with the detached and gnawed con- 

 dition of the bones, is to my mind hopelessly fatal to the hypothesis 

 of a marine submergence. 



(b) The description given in the Introduction (p. 171) of the 

 absence on land-surfaces many miles in extent of the relics found 

 in the fissures, and the extremely limited area of the little pro- 

 montory in which the latter occur, dipping on all sides and covered 

 with materials not found in the fissure, render it impossible for the 

 filling to have been effected simply from above. We may be sure 

 that, whatever might have been the agencies by which the Holmesdale 

 Valley was scooped out, the soft Gault Clay would have given way 

 before the harder Folkestone Beds (as is evinced by the lie of the 

 older gravels), so that a northward extension of a gathering land- 

 surface was truncated. The stream, however, extended over the 

 Gault, and from this source derived the clay which forms a con- 

 stituent of the fissure-material, both disseminated and as water-rolled 



the tooth itself is almost wanting, and is represented by a mere thickening of 

 the labrum. The columella-teeth are not more than one-third the size of 

 those in the recent species, and occur down inside the whorl so as to be in- 

 visible when the shell is viewed obliquely. The peristome is more reflected and 

 less thickened, and consequently less ' toothy,' altogether presenting more the 

 outline of Taludef.tr -ina margmata. — March 20th, 1^94.] 



U. J. G. S. :No. 193. o 



