104 FOSSILS FROM THE UPPER GREENSAND. 



In conclusion, I may remark that this bed of sandstone, and the 

 fossils it contains, should have a special interest for the geological 

 members of our Club, because there is nothing exactly like it 

 elsewhere, and because it is entirely confined to the county of 

 Dorset. It is unusual for a bed of phosphatic nodules to occur at 

 the top of a formation. They are generally basement beds 

 occurring above and not below a plane of erosion, and when a 

 nodule bed in this position also contains a peculiar set of fossils, 

 including some which generally occur in much lower parts of the 

 same formation, the interest attaching to it becomes of more than 

 local importance. 



REMARKS ON SOME OF THE SPECIES. 



Ammonites rhamnonotus, Seeley (1865). Ann. Mag. Nat. Hist., 

 Vol. XVL, p. 233, PI. XL, fig. 7. 



This species was first described by Prof. H. G. Seeley from 

 specimens obtained from the Cambridge Greensand, but derived 

 originally from the Gault, like most of the other fossils in the 

 Cambridge nodule-bed. It has never been recognised elsewhere in 

 England, but was found in France by Prof. Hebert in beds of 

 Gault age (Depmt du Gard), and described by him in 1875 under 

 the name of Am. gardonicus (Ann. Sciences Geol., Tom. vi., p. 113, 

 PI. IV., figs. 1, 2). 



I have compared the Dorset specimens with Cambridge 

 specimens, and with casts of Am. gardonicus given me by the late 

 Prof. Hebert, and find them correspond in every particular. When 

 young, the ribs curve slightly forward in passing over the back, 

 and bear three small swellings or tubercles, one in the middle and 

 one on each side of the back ; these swellings, however, disappear 

 with age, and on the later whorls of a full-grown shell the ribs are 

 nearly straight, passing evenly over the back without any 

 interruption. 



Am. rhamnonotus is a rare fossil at Cambridge, but is not 

 uncommon in the Dorset bed. 



