372 Revieivs — Barrande's Silurian of Bohemia — 



It has, however, very distinctive ornamentation, consisting of strong 

 transverse ridges crossed obliquely by spiral ones, which give rise to 

 oblong tubercles at the^points of crossing. All the species of the last 

 three genera are from Etage D (Ordovician). 



In the family Horiostomidae, Koken, there are recorded four genera, 

 Horiostoma, Mun.-Chalm., Tubina, Barr., Meandrella, Pern., and 

 Spirina, Kayser. The genus Horiostoma is separated from Poleumita y 

 Clarke (Polytropis, De Kon.), with which it lias generally been 

 identified, and is distinguished by having the umbilicus surrounded 

 by a keel, by the rapid increase of the whorls, by the last one being 

 often free, and by its trapezoidal aperture without operculum. It is 

 represented by two species. 



Tubina, Barr., is closely related to Horiostoma, and is chiefly 

 distinguished by having the aperture enlarged like a trumpet, and by 

 being symmetrically coiled. Three species are described. 



Meandrella is created for a species (Euomphalus sculptus, Quenst.) 

 greatly resembling Tubina, but differing in the ornamentation being 

 less developed, in having zigzag transverse lines and in having the 

 aperture less enlarged. The species belonging to the last three genera 

 occur in F-f 2! 



The fourteen species of Spirina described are all confined to Etage 

 E-e 1, and e 2, with the exception of one which is also represented in 

 F-fl. 



The family Calyptraeidae, Koken, in addition to the genus Clisospira, 

 Billings, comprises two new genera of Perner, Paragalerus and Pro- 

 crucibulum. The former is represented by a single species and greatly 

 resembles Progalerus, Holzapfel, but is distinguished by its convex 

 whorls, deep sutures, and ornamentation. 



Procrucibulum contains three species, having a likeness to the genus 

 Crucibulum, Schumacher, but which differ in the length and in the 

 spiral form of their lamellae. 



We now come to the description of the genus Hercynella, Kayser 

 {Pilidion, Barr. MS.), whose affinities have given rise to considerable- 

 diversity of opinion, authors referring it respectively to the Siphonariidae, 

 Fissurellidee, Auriculidae, or the Capulidae. The chief requisite for 

 deciding this question is the discovery of well-defined muscular 

 impressions, and hitherto little of this nature has been observed by 

 Dr. Perner. He places Hercynella in the first-named family, though 

 its habits, according to him, must have been very different from other 

 members of the group. It is especially characteristic of F-f 1 , where 

 it is represented by eight species. He states that the argillaceous and 

 calcareous schists in which it occurs were deposited in warm seas of 

 little or medium depth, and that they Avere certainly not of littoral 

 origin. On this supposition, and taking also into account the thinness 

 of the test, he suggests that it lived a pelagic life. As evidence in 

 favour of its being a pulmonate he quotes that the fold of the shell 

 varies in position in the same species, being sometimes dextral and at 

 others sinistral, and he compares this with the case of certain species 

 of Helix which may be either dextrally or sinistrally coiled. 



Now the recent Siphonaria and its near ally, Gadinia, are eminently 

 sedentary, being attached to rocks in the littoral zone, the former at or 



