KONGL. SV. VET. AKAUEMIENS HANUL. HAND. 19. N:() 6. 67 



rely agrees with it in sluipe and ornamentation. Another common form is similar to 

 Capulus euomplialoides of Mac Coy. Thei'e cannot be much doubt that when the various 

 American species of Platyceras, Platystoma and Strophostylus have been sufficiently 

 throughly examined, they may prove to contain many identical forms. Specimens sent 

 to me from Mr S. A. Millek in Cincinnati as Platystoma niagarense, do not in any 

 sensible degree difter from certain vai'ieties of Platyceras cornutum. This, however, in 

 the European strata never attains such a great size as the American ones. 



As to the geological duration of this species it seems to have continued also 

 during the Devonian e])och, as it probably is identical with or nearly related to the 

 Devonian Pileopsis prisca Goldf. p. p. 



2. Platyceras cornutum, var. loricatum n. 



PI. II, figs. 53—57. 



Shell planorbiform, spire depressed or hidden within the volutions of the large 

 and tumid body whorl. Surface imbricated by transverse, wavy lamina; which project 

 in a thin edge, fig. 58, above the surface, and include tliickset, threadfine longitudi- 

 nal lines. The transverse lamellaj are more distantiated near the aperture than on the spire. 

 The whorls are three or at the highest three and a half, rapidly decreasing in width towards 

 the apex. The aperture is oval or lobate, forming grooves which continue on the body 

 whorl. The sinuosities of the aperture are seen a long way up this wiiorl through the 

 wavy lines of growth. The inner lip is straight, not refiexed. The spire is often so 

 sunk as to be nearer the umbilical side of the shell than the apical. Height 8 millim., 

 breadth 12 millim., in another specimen height 9 millim., breadth, 15 millim. 



This variety whicli by transitional specimens is linked to the preceding, has been 

 found near Nya Slitegards in Dalhem, and in the limestone of Klintcberg. 



3. Platyceras prototypum Phillips. 



PI. Ill fig. 10—18. 



Nerita tspirataf var. 1839. Sow. Sil. Syst., 625, pi. 12 1'. 15. 



1843. MoKRis Catal. 154. 



1848. Bronn Nomenclat., 806. 



Nerita prototypa 1848. Phillips Mem. Geol. Surv. II, 358. 



1854. Morris Catal. 2d Ed., 264. 



Natica Wenlockensiis 1850. D'OiiB. Piodr., 29. 



Acrooidia prototypa 1854. Salter in Siluria 2d Ed., 230 1 



1859. Id. ib. 3d Ed., 548 ) ?'• -'* '• ^■ 



1871. Baily Figures of Cliaract. Brit. P'ossils ]it 111 Gl, pi. X.\I f. 11. 



1873. Salter Catal. Cambridge Foss., 154. 



Strophostylus cyclostoma 1864. Hall p. p. Transact. Albany Instit. vol. IV, 218. 



Cyclonema brevispira 1876. Ferd. Roemek Leth. Geogn. Taf. 14 tig. 14. 



Shell naticiform, globose, with prominent acuminated spire. The ornamentation 

 nearly of the same pattern as in Platyceras cornutum, only finer and denser. There 

 are the same soi't of graduated, wavy, longitudinal lines, and elevated, threadfine trans- 



