THE SLUG AND ITS ALLIES 171 



covered with numerous gills, which give them a velvety 

 aspect. When placed in an aquarium, they lay eggs in 

 gelatinous coils on the hydroid stems. Eolis l is a com- 

 mon genus (Fig. 161). 



Besides the gastropods, two groups of mollusks may be 

 briefly mentioned here. In one group the body is very 



symmetrical, not only 



externally, but also 



internally, which is 



not true of most 



symmetrical gastro- FIG. m. chiton 



FIG. Nil. Eolis (Cra- j A oommon (Trachydermon) 



tina), a nudibranch. P 018 ' apiculatus, the ar- 



Nat. size. Photo, of representative IS Chi- madillo snail. Nat. 



HvingNiimalbyW.H. ^2( Fig . 1 62 ). This ^ ze R c P oto ' ^ 



animal has a sort of 



coat of .mail, since its shell is made up of eight pieces, 

 lying one behind the other, along its back. When removed 

 from the rock or shell on which it rests, it coils up like a 

 pill-bug or armadillo. 



Coordinate with the Gastropoda is the group of Cepha- 

 lopoda. 3 In this group belong the squids and cuttlefishes. 

 They have a large, distinct head, a circle of arms about the 

 mouth, a funnel-shaped foot, and huge eyes on each side of 

 the head (Fig. 163). The squids are the best-known cephal- 

 opods, since they travel in schools in our harbors and are 

 often cast upon the shore after a storm. They can also be 

 obtained in the markets of our coastwise cities, since their 

 flesh is used to a certain extent as food. Cuttlefishes, 



1 Eolis, daughter of Eolus, the god of the winds. 



2 XIT^V, coat, case, covering. 



3 Ke0aX^, head ; TTOI/S, foot ; because the arms or foot are placed around 

 the mouth, 



