70 G. LINDSTliÖM, ON THE SILUlilAN GAÖTKOPOUA AND TTEKOrODA OF GOTLAND. 



nued growth a dit band, ivhich assumes the shape of an eievated keel or aiso a sunk, 

 shallow groove; its inferior margin covering a part of the hack of tlie preceding volution. 



Table of the genera: 



A) Slit band entire, continuous without any openings. 



1. Shell globular, involute, apertural lips wide, trumpet shaped. Slit band 

 broad, sunk. 



Belleroplion Montfort. 



2. Shell disciform, laterally compressed, aperture hastate, whorls in several species 

 not involute, free and not contiguous. Slit band eievated, often forming asharpedged keel. 



Cyrtolites Conrad^) 



B) Slit band always eievated, perforated by a series of oblong openings- Aper- 

 ture many tiraes wider than the volutions, ornamental lines spiral. Shell discoid, in- 

 volute. 



Tremanotus Hall. 



As to the systeuiatic place of this family every one conversant with the eoncho- 

 logical literature is aware that there are few palfeozoic genera on which the opinions 

 of the authors have been more divided and differed rnore widely. For a succinct sur- 

 vey of these varying opinions it is enough to refer to the works of De Koninck^), Meek^) 

 and Waagen*), where a relation is given in full. Bellerophon has been placed amongst 

 the Cephalopoda by its first discoverer Hupsch, by its denominator Montfort, by De 

 France, Mac Coy, Phillips, Portlock and Chenu. It has been considered as one of 

 the Heteropoda by Sowerby, D'Orbigny, Bronn, Deshayes, D'Archiac and Veeneuil^) 

 Phillipi"), Eichwald, Owen'), Salter, Woodwaed**) and Adams. It has been numbered 

 amongst the Gastropoda by Blainville and Valenciennes (as related to Acera and 

 Bulla), Fleming (as Actaaon), De Koninck and Pictet (to Emarginula »comme un lien 

 perdu entré les Emarginules et les Pleurotomaires»), James Hall, Sandberger, (joining 

 them with Pleurotomaria through Porcellia), Meek and Worthen. Among the most 

 recent authors Stoliczka^) hesitates between placing Bellerophon in the Heteropo- 

 da, Opisthobranchiata and Cephalopoda. Ihering^") denies the affinity of the Bel- 

 lerophons to the recent Heteropoda and places them in a family of tlieir own, quite 



^) A new generic type, intermediate between Bellerophou and Cyrtolites is probably formed by tlie spe- 

 cies named B. norvegicus by Bböggeh. in lus »Silurischen Etagen», p. 53. 



^) Animaux fossiles de la Belgique p. 334. 



*) On the affinities of the Bellerophontidfe in Proc. Chicago Ao. Se. Vol. I, p. 9. 



*) Pateontol. Fndiea. Ser. XIII p. 126. 



*) Geol. Transaetions vol. VI, p. 325. 



8) Handbuch der Malacol. p. 285. 



') Paloeontology p. 72. 



^) Manual of Shells p. 201 to Atlantidae, but in the Supplement edited by U. Tåte in 1868 it is placed 

 as a subfamily to the Pleurotomaricie amongst the Haliotidas. 



*•) Paloeontologia Indioa. V. Gastrop. p. 393. 

 "■") Nervensyst. der Mollusken p. 143. 



