KONGL. SV. VET. AKADEMIENS HANDL. BAND. 19. N:0 6. 59 



oldest Gastropod known in Sweden is Metoptoiua Barrundci Linnak.s.sun from the Cam- 

 brian strata of Scania, in the lower portion of the zone of I'aradoxides Tcssini. 



Palseacmsea? solarium n. 



PI. XIX fifr. 3, 4. 



Sliell patelliform, regularly acuminate, apex nearly median or slightly anterior, 

 the outline oblongate from above. Outside of the shell smooth, only concentrically 

 wrinkled at regular distances by larger elevated ridges, the interstices between them 

 being iinely striated by parallel lines. Interiorly there is around the apex a narrow 

 circle of detached muscular scars, visible on the nucleus as delineated in the figure. 

 Height 3 millims., length 6 mm., breadth 4 mm. 



Hitherto two specimens have been found in the red, conchiferous limestone of 

 Sandarfve kuUe. 



Fain. IV. CALYPTR/EID/E Bkodehip. 



Gen. PLATYCERAS Conrad. 



1809 Heliciles Mautix Petrel'. Derbyensia, pi. 40 fig. 43. 



1810 Capulus MoNTFOKT Concli. System. II, 54; though not iiitcuded by him for fossil species, it was 



adopted for such by De Koninck Anim. Foss. de Belgicjue, 331. 

 1812 Pileopsis Lamarck adopted by Sowerby Min. Conchol. vol. VI pi. ()07, 223. 

 1823 Actila Fischer von Waldheim Mem. Soc. Imp. Xaturalistes de Moscou VI, 234. 

 1828 Turbinites Hisinger Anteckniiigar IV, 221. 



1840 Platyceras Conrad Aun. Rep. Geol. Surv. N. Yoik, 205. 



1841 Acroculia (rectius Acrocylia) Phillips Pal. Foss. of Cornwall, 93. 



1842 Platyostoma (reetius Platystoma) Conrad Journ. Acad. Nat. Sc. Philad., 275. 



1843 Orthonychia Hall Rept. 4th Uistr. N. York Gcol. Survey, 172 



1844 Naticopsis Mac Coy p. p. Synops. Carb. Foss. Ireland, 33. 

 1859 Stropliostylas Hall 12th Rept. State Cab. N. York, 20. 

 1859 Ljocct-as Hall Pal. N. York vol III, 330. 



1868 Exogyroceras Meek & Worthen Geol. Survey Illinois, vol. Ill, 608. 

 1878 Capreoltts R. Ethekidge Sr. (lapsu!) Qu. .lourn. Geol. Soc, vol 34, 603. 



Shell globose or naticiform with small, depressed or only moderately prominent 

 spire, last whorl enormously developed, globose or transversally jjrotracted and elongated. 

 Aperture circidar or oval.^ outer lip reflected and enlarged into a thin laminar edge, irhich 

 in well preserved specimens is persistent during the continued growth of the shell and gives 

 the exterior surface a characteristic ornamentation of projecting, thin lamina'. The inner 

 lip of the aperture much varying; sometimes with twisted {«Stroj)hostylus»), sometimes thin 

 and smooth columella {^iPlatyceras'»). No operculum has ever been found. 



In justification of the above list of synonymous genera the following statements 

 of the opinions of various authors upon this matter may be adduced. The earliest 

 description of any fossil belonging to this group is in Martins Petrificata Derbyensia 



