2l6 



GASTEROPODA, 



The Limpets (Patella}, the appearance of which is well known to every 

 sea-side visitor. 



FIG. 228. LIMPET. 



FIG. 229. TUFTED CHITON. 



The Coat-of-Mail Shells (Chiton) are of very remarkable structure: 

 their body is covered by eight overlapping shelly plates, surrounded by a tough 

 leathery margin, often studded with little scales or spines or hairs, under the 

 protection of- which the branchiae are situated. The flexibility of their armour 

 is such, that they are enabled to roll themselves up into a ball, and their head 

 is quite unprovided either with eyes or tentacula. 



ORDER NUDIBRANCHIATA.* 



The animals belonging to this Order are marine slugs, unpro- 

 vided with a shell, and breathing by means of branchiae placed 

 upon their backs, and thus exposed, naked and unprotected, to 

 the influence of the surrounding medium (Fig. 230). 



FIG. 230. CROWNED EOLIS. 



Several species of these naked-gilled Mollusca are common on 

 the British coasts. They exhibit a very great diversity of form, 

 and an extraordinary variety of lively and beautiful colours. The 

 gills are contractile into cavities on the surface of the body, and 



* Nudus, rmcovered ; branchiae, gills: naked-gilled. 



