figured in Phillips's 'Geology of Yorkshire. 1 297 



terior side of the shell. There does not, therefore, appear to 

 be any thing in the structure oiPlatyceras, Conrad, which defi- 

 nitely separates it from Capulus, Montfort. 



The examination of numerous specimens has convinced me 

 that the reduction in the number of species of the British 

 Carboniferous Capuli made by Profs, de Koninck* and 

 M'Coyt is a step in the right direction. 



The latter writer has asked " whether Mr. Sowerby has 

 confounded two species of Pileopsis, and which of them has the 

 best right to the specific name vetusta ?" After a careful 

 examination of Sowerby's specimens, the conviction is forced 

 upon me that two distinct forms have not been described 

 under one name, but that the specimens in the " Min. Conch. 

 Collection" fairly represent the old and young conditions 

 of a single species, Capulus vetustus. It also appears to me 

 that Prof, de Koninck \ has followed the right and proper 

 course in separating the specimen called Pileopsis vetustus 

 by Phillips from that of Sowerby, and uniting with the last- 

 named the Pileopsis trilobatus, Phillips. 



Prof. M'Coy has united with the Conch. (Helicites) auricu- 

 laris of Martin three forms described by Phillips ; and in this, 

 so far as one can judge from Martin's figures, I agree with 

 him. 



It results from the foregoing remarks that we have in the 

 " Gilbertson collection " four species only of Capulus, viz. 

 C. vetustus, Sow. ( = C. trilobatus, Phill.) ; C. tubifer, Sow. 

 (= C '. tubifer , Phill.); C. striatus, Phillips; C. auricularis, 

 Martin (= C. vetustus, Phill. non Sow., C. neritoides, 

 Phill., and C. angustus, Phill.). 



Prof. James Hall has proposed the subdivision of the 

 genus Platyceras, Conrad (=Capidus, Montf.), into three 

 sections ; and a fourth has been added by Messrs. Meek and 

 Worthen. However, as the latter authors have remarked, too 

 much reliance should not be placed on these groups, from the 

 tendency possessed by the component forms to run into one 

 another ; nevertheless they may be found of service in a 

 broad sense. They are : — 



1. Platyceeas, Conrad. — Typical forms with an incurved or 

 spiral apex ; surface concentrically striated, and some- 

 times radiately plicate, rarely spiniferous. Type P. tubi- 

 fera, Sow. 

 The British species of this section are Capidus vetustus, 



* Animaux Foss. p. 332. 



t Brit. Pal. Foss. 1853, fasc. iii. p. 523. 



\ Loc. cit. 



