figured in Phillips's ' Geology of Yorkshire." 1 295 



the general outline of P. vetustus, Sow., and well exemplifies 

 the length to which variation proceeds in this very variable 

 genus. It forms the British type of a condition much more 

 common in the Palasozoic rocks of North America than in those 

 of this country, and is allied to Capulus dumosus, Conrad, 

 and C. multispinosus, Meek, both highly spinose species. 

 It is the 

 Pileopsis tubifer, J. de C. Sow. Min. Conch. 1829, vi. p. 224, t. 607. 



Pileopsis tubifer, Phillips, loc. cit. 



Acroculia tubifer, M'Coy, Synop. Carb. Foss. Ireland, 1844, p. 45. 



? Capulus tubifer, De Ryckholt, Mem. Couronnes Acad. Belg. 1852, 



xxiv. p. 34, t. 1. figs. 7, 8. 

 Capulus tubifer, Morris, Cat. Brit. Foss. 1854, 2nd ed. p. 239. 



Pileopsis striatus, Phillips (p. 224, t. 14. fig. 15). 



The figure of this specimen is tolerably good ; only the strise 

 are not close enough. They are also in parts alternately larger 

 and smaller, and, from being here and there broken and dis- 

 connected, give to the ornament of the shell a somewhat granu- 

 lar appearance. The smaller strias are interpolated from the 

 margin upwards ; and faint indications of concentric lines are 

 to be found on some parts of the surface, especially on the 

 apical region. If the surface of P. striatus was, when perfect, 

 more or less cancellated, it will be the type of a group not 

 hitherto recognized in our rocks, viz. the genus Igoceras, 

 Hall. It is the 



Pileopsis striatus, Phillips, loc. cit. 



Capulus striatus, Morris, Cat. Brit. Foss. 2nd ed. 1854, p. 239. 



Pileopsis neritoides, Phillips (p. 224, t. 14. 

 figs. 16-18). 



Figures 16 and 17 are two views of one specimen, and 

 figs. 18 two views of another example. Fig. 17 is somewhat 

 improved in the region of the inrolled apex. The strong lines 

 of growth are wavy and interspersed with fine strias. Prof. 

 M'Coy appears to have been the only one to draw attention 

 to the similarity existing between P. neritoides, Phill., and the 

 Conchyliolithus (Helicites) auricularis, Martin. So far as an 

 opinion can be formed only from a figure, I must express my 

 entire concurrence in the reference advocated by him. Some 

 forms of this genus, more particularly those described by 

 American authors, show a distinct transition in form towards 

 Naticopsis, M'Coy : with these may be placed P. neritoides, 

 Phill. j for if we compare fig. 16 with that of Naticopsis ellip- 

 tica, on the same plate, we see the general community of 



