334 Mr. J. G. Jeffreys on the recent species of Odostomia 



Crag Mollusca of Great Britain. The difficulty is very great, if 

 indeed it is always possible, to identify fossil with recent shells, 

 the characteristic striae and other markings of so many species 

 being wholly lost or abraded in a fossil state, and the whole 

 structure of the shell being subject in that condition to such 

 chemical and other changes. For example, the Chemnitzia cur- 

 vicostata of the Crag Mollusca is evidently the Turbo indistinctus 

 of Montagu ; but the interstitial striae or punctures in the latter 

 shell were not observable by Mr. Wood. 



I have arranged the localities according to the dates of publi- 

 cation or discovery. 



The generic character of Odostomia may be thus expressed : — 



Odostomia, FL 



Animal elongatum ; caput latum, robustum ; tentacula duo, 

 conica, complanata ; oculi bini, ad basim tentaculorum in medio 

 juxtapositi; sustentaculum depressum, antice latius et trunca- 

 tum ; operculum corneum, subspirale, longitudinaliter striatum, 

 testae aperturam obtegens. 



Testa conoidea seu pyramidalis, anfractibus duobus primariis 

 heterostrophis ; peristoma retro incontinuum, ad basim aperturae 

 subeffusum ; columella subverticalis, denticulo aut plica plerum- 

 que instructa. 



Odostomia, Fl., Macg., Thorpe, Wood, and other modern authors. 



Turbo (pars), Linnaeus, Mont., and other authors. 



Helix (pars), Mont., Turt. 



Voluta (pars), Maton, Rackett. 



Turbonilla (Leach), Risso, Loven. 



Phasianella (pars), Fl. 



Turritella (pars), Fl. 



Odontostoma, Turt. 



Melania (pars), Phil., Forbes. 



Eulima (pars), Phil., Jeffr. 



Auricula (pars), Phil. 



Chemnitzia, D'Orb., Phil., and other authors, 



Parthenia, Lowe, Thorpe. 



Odontostomia, Jeffr. 



Pyramidella (?), Jeffr. 



Pyramis (pars), Br. 



Rissoa (pars), Phil., Br., Recluz, and other modern authors. 



Jaminia (Bruguiere), Br. 



Cingula (pars), Thorpe. 



Eulimella, Forbes. 



A few of the species (viz. O. Rissoides, plicata, unidentata, 

 inter stincta and lactea) are sublittoral, or inhabit the coasts at low- 

 water mark, lurking under loose stones and in the roots of the 

 Corallina officinalis, which are left uncovered by the recess of the 



