1854.] HAMILTON MAYENCE BASIN. 283 



But to resume ; — the increasing brackishness of the water during 

 this period is apparent from these hsts, and by the greater number 

 of land and freshwater shells which are foimd promiscuously dispersed 

 throughout the whole thickness, but in general more abundantly in 

 particular localities. These have evidently been washed into the 

 basin by large freshwater streams, emptying themselves and their 

 contents into the lacustrine basin, and show how the diminished 

 saltness of the water was in part at least occasioned. They also 

 offer an argument in favour of our placing the whole Mayence basin 

 higher rather than lower in the geological scale, inasmuch as amongst 

 the land-shells we find at least four species still living in some parts of 

 Europe, viz. Helix pulchella{M.v\\.), Pupa palustris (Drap.), Pupa 

 variabilis (Drap.), and Clausilia exarata (Ziegl.). 



In addition to these observations, I might also quote the com- 

 parison made by Dr. F. Sandberger between the land and freshwater 

 molluscs of the Mayence basin and those now living, in which he 

 has shown, that, with few exceptions, they have analogous, if not 

 identical, representatives in those of the existing Mediterranean 

 basin. With regard to the genus Helix, Dr. Sandberger observes 

 that, amongst the numerous species of Helix found at Hochheim, 

 the true Mediterranean groups of H. verticillus and H. serpentina 

 preponderate, and amongst those found at Wiesbaden is H. moguntina 

 (Desh.), an analogue of H. splendida. In the group oi Helix ver- 

 ticillus, the fossil species H. verticilloides (A. Braun), H, amplificata 

 (Th.), and H. discus (Th.) must be noticed. 



The following tabular list will show some of the analogies observed 

 by Dr. Sandberger : — 



Recent. Fossil. 



Helix acies, Par^scA = Helix discus, 7%o?w. 



olivetorum = subcellaria, Thorn. 



muralis I 



serpentina > (Italy) = deflexa, A. Braun. 



globularis J 



serpentina, i%- = subcarinata, ^. ^ra?m, 



lens == pbacodes, 7%om. 



lenticula = lapicidella, ^. ^raww. 



scabriuscula = Rahtii. 



rotundata = multicostata, 7%o/n. 



pulchella = pulchella. 



triaria = plicatella, iJezws. 



■I , „ f Brauniorum. 



desertorum = \ Mattiaca 



obvoluta = involuta, TAowi. 



Lefeburiana = ■ Arnoldii, 7'Aom. 



personata = osculum, 7%ow. 



Clausilia macarana = Clausilia bulimoides. 



exarata = exarata. 



But it is unnecessary to quote any more instances*. 

 * Sandberger, Untersuchungen, p. 73. 



