450 [June 26, 



presented the appearance of a very thin concave shell, glossy on its 

 outer surface, with irregular concentric undulations, crossed by 

 longitudinal striEe and fine irregular oblique wrinkles. In the 

 middle of the external margin is a large undulation or sinus. The 

 inner surface, as exhibited by its cast, is of a dull black, the outer 

 surface of the shell being of the colour of horn. Miss Anning in- 

 formed me that these bodies generally occur about the middle of 

 the outer chamber of the ammonite, whence they are obtained by 

 breaking the fossil ; but as this process more frequently destroyed 

 than exposed the object of search, I was unable, during my stay at 

 Lyme Regis, to pi'ocure any tolerably perfect specimens, or to 

 arrive at any satisfactory conclusion as to their nature. 



In 1843, my attention was again called to the subject by finding 

 in a bed of lias limestone, at Temple Grafton and Bickmarsh, 

 near Bidford, in Warwickshire, (a bed remarkable for the variety 

 of fish, plants, insects, and Crustacea which it contains,) several 

 anomalous bodies whose characters were difficult to define. These 

 substances are of a nearly semicircular form, very thin, slightly 

 concave, presenting a small notch at the middle of the straight 

 side, and having their surface covered with irregularly wrinkled 

 lines of growth, concentric to the notch above mentioned. From 

 the same point of departure also proceed fine radiating lines, visible 

 only with the help of a lens. The colour is usually black, but they 

 sometimes present a browner tint, as if from a mixture of calca- 

 reous and carbonaceous matter. The usual diameter is from half 

 to five-eighths of an inch. (See figure c.) 



In speculating on the nature of these bodies, although the black 

 colour seemed to indicate a vegetable origin, yet the concentric 

 lines of growth appeared so evidently allied to the structure of 

 Molluscous shells, that I could not hesitate to seek for their affini- 

 ties among the latter class of animals. Indeed, the general aspect 

 is so much like that of an Orthis, that had they been found in a 

 Palteozoic rock, I should probably have referred them to the 

 Brachiopoda. But on closer examination it was evident, that 

 these bodies were very little, if at all, calcareous, and that though 

 their mode of growth Avas similar to that of shells, yet their com- 

 position was, in great measure, corneous, and probably elastic, like 

 the plate in the genus Laplysia. It seemed, therefore, likely that 

 they were part of the internal organisation of some mollusc, and 

 on comparing them with the bodies before mentioned, as occurring 

 in the Ammonites of Lyme Regis, it seemed not improbable that 

 they were of a similar nature. Now the bed of lias in which 

 these substances occur, contains two species of Ammonites, the 

 A. planorbis, Sow., and another allied to A. Conyheari; and the 

 dimensions of these Ammonites are such as would very well 

 permit the bodies in question to be contained in their outer 

 chamber. The form, too, of the bodies, is nearly that of a trans- 

 verse section of the chamber of the Ammonite, so that they might 

 easily close it in the manner of an operculum. From these con- 

 siderations, the most probable supposition seemed to be, that the 



