UPPER, OR FLINTY CHALK. 197 



53. N'autilus elegans. (vide Grey Marl Fossils, No. 27.) 

 Examples of this species, with the undulating markings but faintly 



expressed, are occasionally found in the chalk; perfectly smooth casts 

 also occur, and these are probably referable to the same, the striae being 

 effaced by accident*. 



Locality. Upper chalk, near Lewes. 



54. Ammonites varicms. {Grey Marl Fossils, No. 30.) f A few ex- 

 amples have been found in the Lower chalk, near Lewes. 



65. Ammonites JVoollgari. Tab. xxi. fig. 16. Tab. xxii. fig. 7. 



Discoidal, depressed, volutions one-third inserted, transversely cos- 

 tated ; costae remote, slightly curved, inclined towards the aperture, 

 terminating on the outer margin in compressed tubercles, or spinous 

 projections ; carene acute, deeply serrated. 



The volutions are generally three or four in number, rather depressed, 

 and ornamented with transverse ribs, that terminate on the outer margin 

 in carinated tubercles, which are elongated into spinous projections in the 

 adult shell (as in fig. 16. Tab. xxi.) In some examples, there are two 

 tubercles on the outer extremity of each rib, and one on the inner 

 margin. The carene is acute, and deeply serrated, the projections being 

 almost angular. 



This elegant ammonite is a rare production of the lower chalk: it 

 varies in size from 0-5 inch, to four or five inches in diameter, and is easily 

 identified by the serrated keel, and the form and disposition of the ribs, 

 and tubercles. 



I have named it in honour of my esteemed fi-iend, Thomas Woollgar, 



* It is probable that the nautihis mentioned by Mr. Parkinson, {Geolog. Trans, vol. v. 

 p. 56.) belongs to this species. It is stated to be nine inches long, six inches deep, and five 

 wide ; the whorls obhque, the back marked with small, closely set, transverse, undulating strife; 

 which agree in their direction with the contour of the shell. 



The obliquity of the spire observable more or less, in almost every example of the 

 chalk nautili, ammonites, &c. is clearly the effect of accidental compression, and has no relation 

 whatever to the structure of the original. 



■f- It may be remarked, that the upper chalk is the most recent formation, in which 

 the shells of the genus ammonites have been discovered ; the ocean which deposited it appear- 

 ing to be the last abode of this tribe of testaceje, no vestiges of their remains occurring in any 

 of the superior deposits, and their recent analogue being unknown. 



