148 hind : carboniferous rocks of isle of man. 
The Poolvash Limestones. 
So far the succession is free from difficulty and easily demon- 
strated, but the white shelly limestones of Poolvash present 
some curious problems, which must be dealt with now in detail. 
Mr. Lamplugh has given a very full and lucid account 
of the stratigraphical side of this question, pp. 208-216, and 
to this I can add practically nothing. 
The Poolvash Limestones have long been known as good 
collecting grounds for fossils, and they occupy about half-a- 
square mile between the Balladoole fault and the out -crop of 
the volcanic series at Poolvash. At the latter place these lime- 
stones, which exist as dome-shaped masses, can be seen to pass 
under the black shales of the Posidonomya beds. Lamplugh 
says, p. 216 : " The most southerly exposure of the limestone 
bosses on the coast occurs just above high water mark on the 
southern side of Poolvash inlet. . . . The Posidonomya 
or black marble beds then completely overlap them to the west- 
ward and southward, occupying a little strip on the upper part 
of the shore, while the lower part is composed of the overlying 
volcanic ash, &c." 
The Poolvash Limestones occur in knolls, or detached 
masses, without any definite bedding planes. The knolls are 
of various sizes, some being diminutive, and when unaltered 
by metasomatic changes are crowded with fossils. 
The fossils belong chiefly to the Mollusca and Brachiopoda. 
Corals are rare, but Dibunophyllids and Lithostrotion Portlocki, 
and Lonsdaleia floriformis occur. 
The Mollusca are represented by many Cephalopods, 
Lamellibranchs, and Gasteropods, all jumbled up together, 
the larger shells filled with smaller forms. The Cephalopoda 
in many cases possess their body chambers, and the bivalves 
often have the two valves in contact, but the valves have nearly 
always slipped, and many are single, indicating an entomb- 
ment after the death of the animal. None of the shells seems 
to be rolled, but it seems impossible to suppose that all the 
forms found together could have been adapted to the same 
