BELLINI : FRESHWATER SHELLS OF NAPLES AND NEIGHBOURHOOlJ. 



35 



give all these forms distinguishing names, for if, on the one hand, an 

 elaborate system of classification provides material for a new Linnaeus, 

 on the other hand — nomina sinescis perit et cognito renitn. We must, 

 therefore, admit a large number of varieties, derived sometimes from 

 an unknown type, and bound together by transitional forms which 

 seem at present to follow no definite law. 



The freshwater shells of Naples may be divided into the following 

 faunulas : — 



(i) Faunula fluviatilis, comprising the forms inhabiting clear 

 rapid streams (Sebeto, Sarno). Here LhnncBa and Planorbis are 

 absent, but the following may be taken : 

 Ancylus fluviatilis 

 Bithynia tentaculata 



Valvata piscinalis 

 Neritina fluviatilis 



Unio requieni 

 Sphceriuin corneum 

 Pisidium casertatium 

 P. 



amnicum 



(2) Faunula lacustris, poor in species (Astroni and Lake Patria) ; 

 the following occur: 



LimncEa stagnalis 



L. palustris 



L. li??iosa 



L. peregra 



Planorbis complanatus 



Physa cofitorta 

 Bithynia tentaculata 

 B. rude?ts 

 Valvata piscinalis 

 Pisidium casertanunt 



(3) Faunula palustris, including two kinds of ground, which 

 may be termed the "station of plants" and the "station of swamps." 

 It is rich in species and comprises the marshes and the channels of 

 the Sebeto: 



Limncea stagnalis 



L. palustris 



L. truncatula 



L. auricularia 



L. limosa 



L. peregra 



Planorbis complanatus 



P. carinatus 



P. subangulatus 



Physa hypnorum 

 Bithynia tentaculata 

 B. boissieri 

 B. rubens 

 Valvata piscinalis 

 Sphcerium corneum 

 Pisidium pusillum 

 P. casertanum 

 P. amnicum 



(4) Faunula fontana, inhabiting still clear waters (P'ountains of 

 Capodimonte, the Villa Nazionale and the Botanic Garden) : 



Limn<2a palustris 

 L. auricularia 

 Planorbis fontanus 

 P. complanatus 

 Physa fontinalis 

 P. hypnorum 



Pseudamnicola macrostoma 

 Bithynia tentaculata 

 B. boissieri 

 B. rubens 

 Pisidium pusillum 



