104 CATALOGUE OF THE MOLLUSCA 
but our object at present is only to point out the most charac- 
teristic forms. The absence of a few species of more extensive 
range may be accounted for by the exposed character of the 
coast. 
Our Catalogue contains altogether 394 species, divided as fol- 
lows :— 
Cephalopoda... oi eee he ccmenrere 6 
Gasteropoda— 
Nudibranchiata, ......... 44 
Pellibranchiata,............ 1 
Inferobranchiata, ......... 
Tectibranchiata, ......... 13 
Pulmonatay vs... siete. a 80 
Pectinibranchiata,......... 92 
Scutibranchiata, ......... 3 
Cyclobranchiata, ......... 12 
Cirrhobranchiata, ......... 3 
—— 249 
Conchifera— 
Palliobranchiata, ......... 1 
Lamellibranchiata, ...... 108 
— 109 
Munigataicustaccestaemiecerc de ccemree: 30 
394 
It may be useful to give an idea of the distribution of these 
into different zones of depth, which we shall now endeavour to 
do by enumerating the most characteristic species in each zone. 
We have adopted the divisions of Professor EH. Forbes, contract- 
ing a little their limits, the better to adapt them to the condi- 
tions observable on our coast. They are as follows :— 
1. Lirrorat Zone.—Between high water-mark and the low 
water of ordinary tides. 
2. Laminarian Zone.—Between low water and 12 fathoms. 
3. CoRALLINE Zonz.—From 12 to 30 fathoms. 
4. Reaton or Deze Water.—30 fathoms and upwards. 
