o 



124 G. LliSIDSTKÖM, ON TIIE 81LUKIAN GASTKoroDA AND rTlOROPODA OK GOTLAND. 



liis Centrifugus. He does not auywhere mentiori it as found in Gotland. I cannot, 

 however, tind tliat Hisingek himself ever in his published writings made any use of 

 the generic name Centrifugus. It occurs only with Bkonn for the first tiine in Lethaja 

 geogiiostica ed. 1, Bd I p- 97, which part of the vohune was published already in 

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

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

 men of which 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 Bkonn names, C. 

 planorbis, is identical with the sulcatus of Hisinger as can be seen by Bronns 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 has not been before observed ^), at once 

 settles the question of its systeraatic 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 scems that De Koninck, 

 Faune Carbonif. de Belgique II, partie III p. 107, intended to give this species the 

 generic name Polytropis instead of Inachus, but as he is citing Euomph. dicors as the 

 typical species, the name Polytropis 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 Fårö. He, however, in the Lethasa unites 

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

 ted tab. I fig. cl c^ 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 Letha3a is 

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



Euomphalus carinatus, Sowerby, identical with the Pleurotomaria described above 

 as P. limata, has also by some English authors been confounded with Pl. planorbis, 

 but it is certainly distinct from it as Murchison ^) also conceded and as has been more 

 pai"ticular]y stated above. 



38. Pleurotomaria helicina n. 



Pl. XI tigs. 34—37. 



Shell discoid, with short, nearly flat spire of five whorls. The slit band is large, 

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

 whorls through the covering, lower edge of the next whorls. 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 



^) "Hisinger 1835 in litteris» he says 1. c. 



-) In auENSTEDT's Petrefiiktcnkunde Deutschlands l:e Abth. 7:r Bd. pl. 200 f. 81 a good delineation 



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

 ^) Qu. Journ. Geol. Soc. 1847 in the Postscript p. 1 to »Siluriau Rocks of Sweden». 



