578 



Geological Society. 



January 5, 1842. — A paper " On the Mouths of Ammonites, and 

 on Fossils contained in laminated beds of the Oxford Clay, discovered 

 in cutting the Great Western Railway, near Christian Malford in 

 Wiltshire." By J. Chaning Pearce, Esq., F.G.S., was read. 



Mr. Pearce commences by stating, that his attention was first di- 

 rected to this part of the railway by the impression of a crushed 

 Ammonite procured at Cheltenham in April 1841, but that he was 

 prevented from examining the locality for three or four months. 



The following section of the beds is given by Mr. Pearce : — 



1. Alluvial soil 2 feet. 



2. Gravel 8 — 



3. Four or five bands of laminated clay, al- 



ternating with sandy clay, almost en- 

 tirely composed of broken shells. ... 6 — 



4. Clay, containing Gryphaa bilobata. 



The objects of the author are, first to draw attention to the organic 

 bodies discovered in the laminated clay ; and secondly, to describe 

 the various forms which the mouth of the Ammonite assumes in dif- 

 ferent species and in different stages of growth in the same species. 



The fossils obtained from the laminated clay are stated to be as 

 follows : — 1. A succulent plant. 2. Lignite, with oysters sometimes 

 affixed to it. 3. Crustaceans, supposed to have inhabited the dead 

 shell of the Ammonite*. The specimen described is stated to have a 

 finely tuberculated and delicately thin covering ; the tail to have 

 the appearance of being divided into three portions, finely corrugated 

 towards their edges ; the body to have on each side internally five 

 or more processes ; and the head to be furnished with several short 

 arms and two long ones jointed a little above the head and ter- 

 minated in two claws, the longer being serrated on its inner edge. 

 4. Another allied crustacean is stated to have also an extremely thin 

 and finely tuberculated covering ; to be furnished with two long arms 

 of similar shape, each terminated at its extremity by one claw, and 

 two others projecting from about the centre, and passing off poste- 

 riorly are two fan-like processes of similar shape. 5. Trigonellites, 

 two species. 6. One valve of a Pollicipes. 7. The remains of an 

 animal considered to have been probably allied to a Sepia. 8. Shells 

 of the genera Unio, Cyclas, Astarte, Avicula, Gervilla, Pinna, Nu- 

 cula, Rostellaria, Turritella, Ammonites f, Belemnites, and an animal 

 to which he has applied (since the paper was read) the name of Be- 

 lemnotheutis. In describing the last fossil, he states that the lower 

 part is conical, blunt at the apex, and chambered internally like the 

 alveolus of a Belemnite, with an oval siphunculus near the edge of 

 the chambers ; that it has a brown thick shelly covering which gra- 

 dually becomes thinner towards the superior part ; that immediately 



* To this organic body Mr. Pearce has given since the paper was read 

 the name of Ammonicolax. 



f Since the paper was written Mr. Pearce has consulted Mr. Pratt's ac- 

 count in the Annals of Natural History for November 184], of Oxford 

 clay Ammonites, and ascertained that he possesses [A. Lonsdalii, A. Bright it], 

 [A. Gulielmi, A. Elizabctheaf\, A. Comptom, and A. Konigii. The fossils 

 included between brackets the author considers to belong to one species. 



