INVERTEBRATE ANIMALS. 29 



Group 84.— Family NERITID^. vyjp.Vv]?, the Sea-snail. 

 The species of Nerita are marine, those of Neritina 

 and Navicella inhabit fresh or brackish water. Esti- 

 mated number of species : recent, 306 ; British, 1 ; 

 fossil, 100. Oolite. 



H Clithon longispina, distinguished by a remarkable 

 development of tubular spines ; and Nerita 

 peloronta, known to the older conchologists by 

 the name of " The Bleeding Tooth." 



^igljtfr ^nhh €nM. 



The Mark ^ indicates specimens or other illustrations exhibited in the cases. 



Sub-order PECTINIBRANCHIATA. pecten, a comb ; 



^payxia, gills. ^ 



Section ROSTRIFEEA. rostrum, a snout; <PspM, I carry. 



Group 85. — Family ONUSTID^ and allies. onus, a load. 

 Estimated number of species : recent, 158 ; British, 3 ; 

 Fossil, 75. From the Carboniferous upwards,, 



^ Examples of Oniistus, Calyptra, Crepidula, 

 Narica, dc, shewing the characters which have 

 suggested the popular names, Cup-and- Saucer 

 Limpet, Slipper-Limpet, Bonnet-Limpet; the 

 Mineralogist Carrier, Conchologist Carrier, &c. 



Group 86.— Family TURRITELLID^ and allies. turris, 

 a tower. Estimated number of species : recent, 124 ; 

 British, 3 ; fossil, 200. Tertiary. 



II Examples of Turritella, Vermetus, Ccecum, Sili- 



quaria, Siphonium, dc. 

 In Vermetus, the whorls of an ordinary spiral 

 shell are seen disunited, and taking the 

 form of a cork-screw. 



