Vol. 52.] OF THE CHALK ROCK. 97 



EXPLANATION OF PLATES II.-IV. 



[All specimens from the Chalk Kock.] 



Plate II. 



Figs. 1, 2. Ptychoceras Smithi, sp. nov. Cuckhamsley. Montagu Smith Col- 

 lection, Woodwardian Museum. 1. x3. 2. Suture-line, X about 6. 



3-5. Heteroceras Reussianum (d'Orbigny). 3. Portion of one of the later 

 whorls. Luton cutting. Coll. Dr. Morison. Nat. size. 



3 a. Section of whorl of the same. 



4. Base of later whorl. Cuckhamsley. Montagu Smith Collection. Nat. 



size. 



5. Suture-line of a specimen in the collection of Dr. Morison. Luton 



cutting. X 4. 

 6-8. Heteroceras, sp. 6. Luton cutting. Coll. Dr. Morison. Nat. size. 

 7 a, b, c. Cuckhamsley. Montagu Smith Collection. Nat. size. 

 8. Suture-line of specimen, fig. 7. X 4. 

 9-10. Baculites bohemicus, Fritsch and Sehlonbach. Cuckhamsley. 



Montagu Smith Collection. 9 a, siphonal side ; 9 b, lateral ; 9 c, lateral ; 



9 d, section, nat. size. 10. Suture-line, X 4. 

 11. Prionocychis Neptuni (Geinitz). Suture-line. Dunstable. Museum 



of Practical Geology, Jermyn Street. Enlarged. 



Plate III, 



Figs. 1-4. Prionocychis Neptuni (Geinitz). 1. Portion of last whorl. Cuck- 

 hamsley. Montagu Smith Collection. Nat. size. 



2. Dunstable. Museum of Practical Geology. Nat. size. 



3. 3 a. Cuckhamsley. Montagu Smith Collection. Nat. size. 



4. Section of whorl. Luton cutting. Coll. Dr. Morison. Nat. size. 

 5-7. Scaphites Geinitzi (d'Orbigny). Cuckhamsley. Montagu Smith 



Collection. 5, 5 a, small specimen with projecting lip, nat. size ; 

 6, 6 a, medium-size specimen, nat. size ; 7, suture-line, X 5. 



8-10. Crioceras ellipticum (Man tell). 8. Cuckhamsley, Montagu Smith 

 Collection ; 8 a. Section, nat. size. 9. Luton cutting, coll. Dr. Mori- 

 son, nat. size ; 9 a. Section. 10. Suture-line, Luton cutting, Museum 

 of Practical Geology (J. Pv. 2270), X 3. 



11, 12. Trochus Sehluteri, sp. nov. Cuckhamsley. Montagu Smith Col- 

 lection. 11. Drawn from a wax mould, X 1^. 12. Base of an imperfect 

 specimen, X 1£. 



13, 14. Pleurotomaria (Leptomaria) perspectives, Mantell. Cuckhamsley. 

 Montagu Smith Collection. 13. Portion of a whorl seen from above, 

 X 2. 14. Base of a small specimen, nat. size. 



Plate IY. 



Fig. 1. Pleurotomaria (Leptomaria) perspectiva, Mantell. Cuckhamsley. Mon- 

 tagu Smith Collection. The largest specimen seen in the Chalk Eock. 

 Nat. size. 



2-4. Trochus berocscirense, sp. nov. Cuckhamsley. Montagu Smith Col- 

 lection. 2. Drawn from a wax mould, X 1-J. 3. Outline of a specimen, 

 nat. size. 4. Base of a specimen, X l£. 



5-8. Turbo Geinitzi, sp. nov. Cuckhamsley. Montagu Smith Collection. 

 5. Nat. size ; the ornamentation is taken from a wax mould. 6. Speci- 

 men showing aperture, nat. size. 7. Base, nat. size. 8. Ornamen- 

 tation of base, X 2£. 



9, 10. Turbo gemmatus, Sowerby. Cuckhamsley. Montagu Smith Col- 

 lection. 9, X 2 ; 10, X \\. 



11. Cerithium cuckhamsliense, sp. nov. Cuckhamsley. Montagu Smith 

 Collection. Nat. size. 

 Q. J. G. S. No. 205. h 



