124 G. LINDSTROM, oN THE S11,11KIAN GASTROPODA AND I'TKROPODA OF GOTLAND. 



his Ceiitrifugus. He does not Jiiiywliere iiieiition it as f'oimd in Gotltmd. I eunnot, 

 however, find that Hi.singkr himself ever in his piiblislied writings made any use of 

 the generic name Centrifugus. It occurs only with Bkonn for the first time in Letluca 

 geognostica ed. 1, Bd 1 j)- 97, which part of the vohime was published already in 

 1835 as may be concluded by referring to the half yearly Catalogue of the German 

 booksellers for that year. This genus included Centrif. costatus His., the type speci- 

 men of wliich is kept in the Cabinet of the School at Wisby and certainly is the shell 

 of a Cephalopodan, probably a Trochoceras. The second species which Bronn names, C. 

 planorbis, is identical Avith the sulcatus of Hisinger as can be seen bj' Brunns Nomen- 

 clator p. 256'). But already in 1837 in the Letha^a Suecica Hisinger gave it the 

 name Inachus. As this name in 1798 had been bestowed on a crustacean by Fabricius, 

 it could not be retained even if the fossil did form an independent genus. The pre- 

 sence of the characteristic slit band, which lias not been before observed ^), at once 

 settles the question of its systematic place. It must, however, be conceded, as has 

 been pointed out above in the description, that there are some features in the position 

 and structure of the band, which remind of Euomphalus. It seems that De Koninck, 

 Faune Carbonif. de Belgi(|ue 11, partie HI p. 107, intended to give this species the 

 generic name I'olytropis iiistead of Inachus, but as he is citing Euomph. dicors as the 

 typical species, the name Polytrojus must be identified with Oriostoma, of which 

 see below. 



In 1831 Hisinger gave the figure of his Euomph. substriatus, Anteckningar V, 

 tab. I fig. e, which as far as can be seen, without access to the unknown type speci- 

 men, is a species of Trochoceras found at Faro. He, however, in the Lethtea unites 

 this form with In. sulcatus, giving it as the und)ilical side. Now a glance on the ci- 

 ted tab. I fig. d (^'- e, is convincing that both d and e are apical sides of different shells 

 and he must himself have been aware thereof, as the latter figure in the Lethiea is 

 drawn in a reversed position, so as to match the apical side. 



Euomphalus carinatus, Sowerby, identical witli the Pleurotomaria described above 

 as P. liinata, has also by some English authors been confounded with PI. [)lanorbis, 

 but it is certainly distinct from it as MuRCHisON ^) also conceded and as has been jnore 

 particularly stated above. 



38. Pleurotomaria helicina n. 



PL XI figs. 34—37. 



Shell discoid, witli short, nearly fiat spire of live whorls. The slit band is large, 

 placed beneatli tlie median line of the body whorl, hidden from view on the other 

 whoi'ls through the covering, lower edge of the next Avhorls. The crescents are obscure, 

 distantiated. The surface is smooth and glossy with some few, indistinct transverse 

 grooves and lines of growth, which are curved backwards. The aperture is nearly 



^) oHisiNGER 1835 ill littuiis« he says 1. c. 



-) 111 Quensi'kdt's I'etrefaktcnkuiide Deutsclilands l:e Abt.li. 7:r Bd. ])l. 200 f. 81 a good delineation 



shows the slit band, but this has not been reraaiked by him in the letterpress. 

 ^) Qu. Journ. Geol. Soe. 1817 in the Postscript p. 1 to "Silurian Eocks of Sweden". 



