594 
ting, the author thinks, probably the situation of the mouth. With 
reference to the first part of the paper, Mr. Pearce also notices an 
animal allied to Sepia or Loligo, one side being covered by a pen 
resembling that of the Loligo, and having immediately underneath 
it, at the junction of the middle with the lower third, an ink-bag 
resting on what resembles a sepiostaire. He mentions likewise ten or 
twelve species of fishes, but without giving names ; also coprolites. 
2. Respecting the form of the mouth of the Ammonites and the 
changes at different periods of growth, Mr. Pearce states his belief, 
that the terminal lip or mouth has a different shape in the young 
shell of almost every species, but assumes in the old’a straight out- 
line, and that he has been aware of this circumstance several years. 
Of cases of young shells with differently shaped lips, he mentions 
Ammonites Brongniarti (Inf. oolite), A. sublevis (Oxf. clay), A. ob- 
tusus (Lias), A. Kenigii (Kelloway Rock, the mature shell is stated 
to have a straight mouth), A. Calloviensis (Kelloway Rock, the lip of 
the old shell is stated to be slightly contracted and to terminate with 
gently undulating sides), 4. Walcottii (Lias), and A. Goodhalli, fur- 
nished in the mature state with a single horn-like projection at the 
front of the mouth. In addition to these species he enumerates those 
noticed in the preceding part of the paper. Mr. Pearce is further of 
opinion that at different periods of the formation of the shell the la- 
teral processes were absorbed and reproduced, and that therefore 
they are found in various stages of growth, but are invariably want- 
ing in the mature shell. In some species in which the successive 
mouths were much contracted or expanded, the new shell the author 
says was continued without the absorption of the lip, leaving a highly 
projecting rib or a deep furrow”. 
After a careful examination of upwards of twenty species in his 
collection, with perfect mouths of all ages and from different strata, 
not including the Oxford clay, Mr. Pearce has found the external 
chamber to vary considerably in extent, occupying in some speci- 
mens the whole of the last whorl, but in others less than one-third, 
and without reference to age or species; and he therefore suggests 
that the young animal of the Ammonite filled the whole of the outer 
chamber, extending also to the extreme points of the lateral pro- 
cesses in those species which were provided with them ; and thereby 
not only received support but afforded protection to a portion of the 
shell extremely liable to injury. In old individuals he is of opinion 
that the animal when quiescent was entirely contained within the 
last chamber. ; 
At the Meeting held on the 15th of Dec. 1841, portions of the 
stems and other parts of Cyathocrinites quinquangularis, C. planus ; 
Platycrinites levis, Rhodocrinites verus, Actinocrinites triacentadac- 
tylus and Poteriocrinites from the mountain-limestone of Preston, 
were presented by Mr. Gilbertson to illustrate certain characters de- 
scribed by the late Mr. Miller in his work on Crinoidea; also spe- 
cimens of a species of Aulopora from the same formation. 
* The author was not acquainted with M. Al. d’Orbigny’s work, Pad. 
Francaise, when he wrote the paper, and was not aware of the views given. 
in it respecting the mouth of the Ammonite. 
