'1 BRANCH MOLLUSI .\. 



ORDER SCAPHOPODA (skaf o po'da). 



The Tooth-shell is one of the lowest forms, and, in 

 Fm . 60 . many points of its structure, resem- 



bles the Acephals. The shell, long 

 Dent<Ttium denta a*. and tusk-like, is open at each end 



Tooth-shell. ,-, . , 



alJ owing the animal to reach out its 



tentacles and burrow in the sand, while pure salt-water 

 enters the small aperture at the apex. 



ORDER POLYPLACOPHORA (pol I pla kof'6 ra). 



The Chitons (ki'tunz) may FIG. 01. 



be spoken of as many-valved 

 Univalves, as they are true 

 cephalophorous (sef a lofo rus) 

 mollusks in their structure, 

 though the limy covering of 

 the mantle is divided into sev- 

 eral segments. Chitons in- 

 liiihit all rocky coasts, where 

 they securely attach them- 

 selves, even during severe 



Chi' ton el' f gems. Chiton. 



storms, by their broad suck- 



ing foot.* There are numerous species, and to locate 

 them precisely in their relations to other mollusks, has 

 given Naturalists much trouble. 



ORDER NUDIBRANCHIATA (nu di brang ke a'ta). 



The Nudibranchs (nu'di brangks), [Doris], are marine 

 forms, often of great beauty. They are termed "Naked- 

 gilled " Mollusks, in that the organs for purifying the 



* Some species are now known to have their entire dorsal surface beset with 

 visual organs, it being estimated that 8,000 are borne by a single individual. 





