AMMONITES. 43 



30. Ammonites Icenicus, Sharpe. Plate XIX, fig. 4. 



A. testa discoided, compressd, lavi, inornatd : anfractibus paucis : umbilico mediocrt 

 dorso rotundato : aperturd ovatd : septorum lobis laleralibus, primo trifido, cceteris incs- 

 qualiter bifidis. 



Shell discoidal, smooth ; with few whorls, flattened on the sides, and rounded on the 

 back : umbilicus of middling size, allowing two fifths of the inner whorls to be seen ; 

 aperture ovate : septa with four lateral lobes, the first trifid, the others unequally bifid. 



Diameter, 2 inches ; height of last whorl, 1 inch ; width of aperture, | inch. 



Rare in the Upper Chalk near Norwich. 



The Ammonite here described has few characters by which it can be distinguished, and 

 may perhaps prove to be only a young shell. But the Upper Chalk contains so few 

 Ammonites, that it is desirable to place on record all that are known. It belongs to the 

 same group as A. Lewesiensis. 



31. Ammonites Deverianus, UOrbigng. Plate XIX, fig. 5. 



Ammonites Deverianus, If Orbigny . Paleont. Franc. Terr. Cret., t. Ill, figs. I and 2. 



A. testa inflatd, transversim tuberculato-costatd : anfractibus paucis, lateribus com- 

 pressis, dorso rotundalis ■■ costis incequalibus, simplicibus vel bifurcatis, 9 tuberculatis : aper- 

 turd quadrato-rotundatd : umbilico magno. 



Shell discoidal ; with few whorls, flattened on the sides, and rounded at the back, 

 crossed by numerous tuberculated ribs, which are continued over the back -. about half the 

 ribs commence at a tubercle on the edge of the umbilicus, and are either simple or bifur- 

 cating ; between these there is often a shorter rib, commencing on the middle of the side 

 of the whorl ; all are equal on the back : tubercles large and round, in nine rows ; viz., 

 three on each side, and three on the back ; the dorsal rows containing about twice as many 

 as the umbilical row : umbilicus very large, leaving nearly two thirds of the inner whorls 

 visible : aperture nearly square, with the corners rounded off. 



Diameter, 4 inches ; height of last whorl, If inch ; width of aperture, If inch. 



From the Grey Chalk of Sussex. The only specimen seen is in the British Museum, 

 from the collection of F. Dixon, Esq. It has been found in France in the " Craie Chlo- 

 ritee " of Uchaux. 



This species is readily distinguished from all others by the number and position of the 

 tubercles. 



