330 -Dr. Maton's Description of 



ought to be placed, for Linnaeus has not made the absence of 

 teeth an indispensable character for a Mytilus, and some of that 

 genus gape hke the Myce at one extremity. 



5. VOLUTA FLUVIATILIS. 



Tab. XXIV. Fig. 13. 



VoLUTA testa subovali, pelliicida, laevi, columella biplicata, 

 apertura integra. 



Habitat in America australi, fliiviatilis. 



Testa vix ^ poll, longa, ultra i poll, lata, tenera, flavescente-vi- 

 ridis, maculis brunneis transversim lineato-notata. Anfractus ro- 

 tundati. Spira prominula. 



6. VoLUTA FLUMINEA. 



Tab. XXIV. Fig. 14, 15. 



VoLUTA testa obovata, cornea, longitudinaliter delicatissimti 

 striata, apertura integra, columella biplicata, apice acuto, bre- 

 vissimo. 



Habitat in America australi, fluviatilis. 



Testa magnitudine precedentis, at ventricosior, anfractibus 

 magis depressis, apice ver6 tenuior, colore pallidior, obsolete li- 

 neato-maculata, lineis distantioribus. 



These VobdcE are so nearly allied to each other, that I hesitated 

 at first to consider them as distinct species ; yet the characters 

 given above, it is presumed, will sufficiently authorize their se- 

 paration. The shape of V. fluviatilis is almost a perfect oval, 

 but that ofV.flumineuis obliquely ovated. This variation might 

 be attributed to difference of age, were not the specimens all of 



equal 



