38 Reviews — Dr. G. Lindsfroin's Silurian Gasteropoda, etc. 



P. Lloijdii, Sow., P. hicinctn, Hall, BelleropJwn trilolatus, Sow., 

 Loxoneraa sinnosum, Sow., Onostoma discors, Sow., 0. rugosum, Sow., 

 0. scidptum, Sow., and Cyclonema carinatnm, Sow. Four species also 

 occur in the corresponding strata in North America, but none in 

 Bohemia. 



With the exception of the genus Chelodes, which belongs to the 

 CTiitonidcB, and the genera Subidites, Euchnjsalis, and possibly 

 Onychochilus, which, judging from their apertural characters, belong 

 to the Siphonostomata, the Gotland Gasteropoda are included in the 

 Holostomata. Twelve recent families are probably represented ; 

 but there is some doubt whether the forms which have been referred 

 to the Litorinidge, Pyramidellidee, and Turbinidee rightly belong to 

 these groups. Of the twenty-five genera, only two, Pleurotomaria 

 and Trochus, still i-emain in existence. Though Pleurotomaria had 

 not yet attained the maximum development which it reached in 

 Jurassic times, yet even here, in conjunction with MurcMsonia, it 

 forms about one-third of the species. Some degree of uncertainty 

 inevitably attends the affinities of many of the Silurian Gasteropoda to 

 recent forms with which they have been associated, but there are 

 some in which the resemblances are too striking for any doubt to be 

 felt respecting their real relationships. Thus, forexample, the muscular 

 scars on the interior of Tryblidium, Linds., clearly prove its alliance 

 with the Patellidge, and the Oriostomata show by the operculum and 

 the nacreous inner layer that they can be safely included in the 

 Turbinidse. 



The author thinks that the worn and abraded condition of many 

 of the shells and the presence of members of the Chitonida3 and 

 Patellidas indicate a littoral character for the fauna, and from the 

 presence of PleiirotomaricB, Trochi, and the large Pteropods, that it 

 existed under tropical conditions. 



The greatest number of species of Gasteropoda recorded from 

 Gotland by previous writers did not exceed 23. Murchison, in his 

 paper,' " On the Silurian Eocks of Gotland," only enumerates 9 

 species, whilst Dr. Bigsby in the " Thesaurus Siluricus " catalogues 

 30 ; but some of these are synonyms and others arose from tlie 

 curious mistake of supposing that the word ' Steinkern,' which 

 appears in Helmersen's list after some of the genera, really meant 

 the specific name. 



The remarkable increase in the number of the species described in 

 this volume is owing to the abundant materials which, through care- 

 ful collecting for a long series of years, have been gradually 

 accumulating in the Swedish State Museum of Natural History at 

 Stockholm, where the typical forms are now preserved. 



We can only comment very briefly on the detailed descriptions of 

 tne genera and species which have been thoroughly worked out by 

 the author in such a careful manner, that whatever opinions may be 

 held as to the names and systematic position of the various species, 

 there can be no difficulty in their identification. 



Commencing with the Pteropoda, five species of Conidaria are 

 ^ Quart. Journ. Geul. Soc. 1847, p. 29. 



