250 



SYSTEMATIC ZOOLOGY 



never interfere with one another, but a thin partition of wood is 

 always left between. They have done great damage to wharves 

 in both Europe and America. Their tubes are sometimes as 

 much as twenty-five centimeters in length and a centimeter in 

 diameter. In the Philippines an allied genus occurs which 

 bores in the sand only ; the body is five centimeters in diameter 

 and but little short of two meters long. 



CLASS V. CEPHALOPODA 



The Cephalopoda (Gr. fcefaiX/], head, and 7rou?, foot), while 

 unquestionably belonging to the type Mollusca, constitute an 



isolated group without any close 

 relationship to the other classes. 

 They include such animals as the 

 nautilus, octopus, cuttlefish, and 

 squid, all exclusively marine, and 

 found along the shore or swimming 

 near the surface in the open ocean, 

 or in the case of the larger species 

 living at considerable depths. The 

 bod}- is bilaterally symmetrical, and 

 there is a head marked off from 

 the rest bx a slightly narrower 

 region or neck. This head has a 

 circle of armlike processes, some- 

 times bearing tentacles, sometimes 

 hooks, or suckers, and to be re- 

 garded as homologous with a part 

 of the foot in other Mollusca. In 

 the center of these tentacles is a 

 depression, at the bottom of which 

 lies the mouth. It is provided 

 with two strong, chitinous jaws, 

 resembling the beak of a parrot, 

 and within is a typical radula. 

 The head also bears a pair of eyes, 

 usually very highly developed, as 

 well as otocysts and often olfactory 



Fro. 260. Sepia cultrata. A New Zea- 

 land cuttlefish ; dorsal aspect. (After 

 Parker and Haswell.) 



organs. 



