270 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [Dec. 14, 



condition of the bones indicates that the soft parts had time to decay 

 before the specimens were buried by the addition of new layers of 

 vegetable matter and sediment. I account for these appearances, by 

 supposing that this tree, like other erect Sigillarice in this section, 

 became hollow by decay, after being more or less buried in sediment ; 

 but that, unlike most others, it remained hollow for some time in the 

 soil of a forest, receiving merely small quantities of earthy and ve- 

 getable matter, falling into it, or washed in by rains. While in this 

 condition it may have served as a place of shelter to the animals 

 found in it, or may have been too deep to permit their escape when 

 they fell in by accident. Possibly it was a place of residence for the 

 snails and myriapods, and a trap and tomb for the reptiles ; though 

 the coprolitic matter in some of the layers would seem to indicate 

 that these last in some instances were able to subsist for a time in 

 this underground prison. The occurrence of so many skeletons, 

 with probably more than a hundred specimens of land-snails and 

 myriapods, in a cylinder only fifteen inches in diameter, proves that 

 these creatures were by no means rare hi the coal-forests, though 

 they have left so few indications of their presence in other beds. 

 The existence of vertical hollow stumps in such a condition that air- 

 breathing creatures could reside in or fall into them, implies that 

 the soils of the Sigillarian forests were not always so low and wet as 

 we are apt to imagine. 



§ 2. Carboniferous Land-Snail — Pupa vetusta, n. s. (Figs. 1-3.) 



An imperfect specimen of this shell, found in 1851, was described 

 by Sir C. Lyell, and its structure figured, in the Quart. Journ. Geol. 

 Soc. vol. ix. pi. 4. The numerous specimens which I now possess 

 enable me to present a complete restoration of its form, and to state 

 that it falls within the limits of the genus Pupa. It may be described 

 as follows : — 



Cylindrical, but tapering towards the apex ; surface shining, mi- 

 nutely marked with longitudinal rounded ridges ; whorls eight or 

 nine, rounded, width of each whorl about half the diameter of the 

 shell ; aperture rather longer than broad ; outer lip regularly rounded 

 and reflected at the margin ; pillar-lip straightish above, rounded 

 below. Edentulous ; length ^-ths of an inch, or a little more. 



I obtained in all about fifty specimens more or less complete of 

 this shell from the interior of this trunk, and many others must re- 

 main concealed in the matrix. There were also numerous frag- 

 ments of shells that had been broken and partially decomposed, as if 

 this hollow stump had long served as a harbour for land-snails. It 

 is very probable that they formed a part of the food of their reptilian 

 associates, and some may have been introduced by them. I have 

 found in the stomach of a specimen of Menobranchus lateralis not 

 six inches in length, as many as eleven unbroken shells of Physa 

 heterostropha. The coal-reptiles and batrachians may have devoured 

 their contemporary pulmonates in similar quantity. 



Where so many examples of one species of pulmoniferous mollusk 



