30 INVERTEBRATE ANIMALS. 



development of tubular spines. Nerita pelo- 

 ronta, known to the older conchologists by the 

 name of " The Bleeding Tooth," was found by 

 the writer on rocks dried and intensely heated 

 by the sun. 



dBigljtlj Cable (las^ 



Sub-order PECTINIBRANCHIATA. pecten, a comb ; 



/3/3ayx'«» gills. 

 Section ROSTRIFERA. rostrum, a snout ; <^spw, 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. 



IT Examples of Onustus, Calyptra, Crepidula, 

 Narica, &c., 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 TURRITELLIDiE and allies, turris, 

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

 British, 3 ; fossil, 200. Tertiary. 



IT Examples of Turritella, Vermetus, Ccecuin, Sili- 



quaria, Siphonkim, kc. 

 In Vermetus, the whorls of an ordinary spiral 

 shell are seen disunited, and taking the form 

 of a cork-screw. 



Group 87.— Family AMPULLARIIDiE and allies, ampulla, 

 a globular vessel. Estimated number of species : 

 recent, 181 ; British, 6 ; fossil, 70. Tertiary. 



This family includes the so-called Apple-snails, 

 though differing widely from the true snails, 

 which have lungs and are without opercula. 



