180 
THE GEOLOGIST. 
it, but I believe lie thinks so, and it is a very excellent suggestion— 
for the shape is very like * 
But in the lower part of the coal-formation, and m one or two 
beds also in the upper portions, there are none but truly sea-sheUs. 
It would take long to enumerate them ; but I need only mention 
one or two famihar names. Avicula, or rather a shell between Avicula 
Fig. 6.—Avieulopecien papi/raceus, Sow. 
Fig. 7.— Goniat'deg Listeri, Sow. Fig. 8. — Froductus semiretieulatus, Martin. 
(the pearl oyster), and Peden (the scallop), and therefore called 
Aviculopeden, fig. 1. Goniatites, fig. 2, a shell which is a near relation 
to the nautilus. The nautilus itself is common enough. Nucula, 
a true sea-shell, is with them; and, to name no more, the Procludus 
(fig. 3), which is found everywhere in the mountain hmestone, must 
have been deposited in sea-water — and deep sea, too — for it is found 
with corals and fish, sea-faus and sea-Hlies ; and belongs to a group 
of shells which never quits the open sea. 
Perhaps we need not dwell upon the shells any more ; suffice it 
that those of the bottom of the coal-measures are all marine, and 
those of the top parts are not much like freshwater ones, and from 
the company they keep, were probably marine too. 
* THs author, Endolph Ludwig (Dunker and Meyer's Palaeontograpliica, vol. 
8, pi. iv., V. ; and vol. 10, pi. Ixxi., Ixxii.), in his papers on .the "Naiades of the 
Coal Measures of Westphalia," thinks he has detected the freshwater shells 
Cyrena, Anodon, TJnio ; all of which are, I beheve, Antliro.cosia. ; and also Dreis- 
sena,^ one of which at least is an Anthracomya. He also quotes Planorbis ! but 
the little shell which goes under this n^me is the Spirorhis, mentioned further on. 
