GREY CHALK MARL. 109 



appellation, I have named it after my excellent friend James Parkinson, 

 Esq. M.G.S. &c. of Hoxton Square, the learned author of the " Organic 

 Remains of a former World." 



The specimens figured, although differing from each other in certain 

 particulars, are evidently casts of the same species ; the differences ob- 

 servable arising partly from compression, and from the markings of the 

 original shell being more strongly impressed in some examples, than in 

 others. 



In figures 1 and 5, which are different views of the same specimen, 

 the wreaths are nearly smooth, with the exception of a few imperfect 

 costse. 



Figures 2 and 4, are nearly flat from compression, and the ribs 

 almost effaced, but the surface is covered with transverse strise. The 

 collection of the Geological Society contains a large specimen of this kind 



Fig. 6. A cast of five wreaths, including the venter ; but the outer 

 lip and base of the columella are not preserved. In this example the 

 upper volutions are smooth ; the two lowermost exhibit the ribs and strice- 



Fig. 10. Represents a cast of the dorsum, or back of the shell; but the 

 base of the largest wreath is unfortunately destroyed. In this specimen 

 the ribs and striae, with the styloid process of the outer hp, are well 

 defined. 



Localities. Hamsey, Middleham, Southbourne, Eanscombe. 



] 8. Trochus ? Tab. xviii. fig. 7. 



The outhne of this delicate cast resembles that of Trochus agglutinans 

 of Brander. 



Locality. Hamsey. 



19. Trochus ? Tab. xviii. fig. 9. 



Discoidal, base slightly convex, the margin acutely angular, aperture — ? 



The base of the shell delineated in the figure, is the only portion I 

 have seen ; the angular margin is a remarkable character by which this 

 species may be readily identified*. 



* In a specimen of Ti-ochus agglutinans, from Grignon, recently presented me by M. 

 Brongiart, the outer margin of the last whorl very closely resembles that of the present 

 fossil. 



