UPPER, OR FLINTY CHALK. 199 



Depressed, volutions exposed, quadrangular; disk concave, ex- 

 panded ; ambit broad, oblique ; a row of large obtuse tubercles on the 

 outer margin. 



The volutions are three in number, almost entirely exposed ; their 

 outer margin elevated, and crested with a row of large nodular projec- 

 tions. The ambit is broad, and smooth, inclined outwards, forming an 

 obtuse angle with the inner surface of the volutions. The septa are 

 numerous. 



It is probable that this is the species described by Mr. Parkinson, as 

 being " of a large size, with nodular projections on the sides towards the 

 back, which is generally flat." (Geolog. Trans. Vol. i. p. 559,.) 



The specimen is nearly three and a half times the size of the figure. 



LocaUty. Lower chalk, near Lewes. 



58. Ammonites rusticus. Min. Conch. Tab. 177. 



Depressed, volutions few, gibbous, exposed, with a row of conical 

 tubercles on each side, and two rows on the back ; aperture wider than 

 long. 



The whorls seldom exceed three in number. The bases of the larger 

 tubercles almost touch each other, and expand nearly across the volu- 

 tions. The back is broad, and rather flat ; the tubercles upon it are 

 numerous, and but httle elevated. The inner side of the aperture is 

 concave. 



This species is of frequent occurrence in the lower chalk at Souther- 

 ham, but the specimens are very imperfect. The fossil figured and 

 described by Mr. Sowerby, is more distinct than any that have been found 

 in Sussex. 



This ammonite corresponds in some particulars with A. catinus, but 

 is distinguished by the two dorsal rows of tubercles, and the gibbous form 

 of the volutions. 



Locahty. Lower chalk, near Lewes. 



59. Ammonites Lewesiensis. Tab. xxii. fig. 2. 



Depressed, umbiUcus minute; volutions wide, flat, almost entirely 



