110 WEST COAST SHELLS 



end, while at the other it is narrow, thin and crooked. 



The outer coat shows many concentric strise, but 



this is easily rubbed off, revealing the inner layer, 



which is quite pearly. 



Lionsiella alaskana^ Dall, the 

 Alaska Lyonsiella, is shown 

 in Figure 87. The specimen 

 here represented was dredged 

 from deep water in the Gulf 

 of Alaska. The figure is some- 

 what enlarged, but it shows 

 the main external features of 



Fig. 87. X S (*) 



this thin and delicate shell. 

 As you walk among the rocks when the tide is 

 out you can often find many strange forms of life. 

 On the top of the rocks, so as to be exposed to the 

 sunlight, are mass.es of seaweed, often harboring 

 and concealing various living things. In the caves 

 under the rocks grow quite different animals. Some 

 of them can walk or crawl, and are comparatively 

 easy to classify, while others form mats or cushions 

 and seem to have little in common with ordinary 

 animal forms. One ot these thin mats, often bril- 

 liantly colored, is really a kind of sponge. Another 

 and thicker one, yellowish in color, smooth and firm 

 to the touch, is really a mass of low animal forms 

 and is known as a compound Ascidian, or group of 

 Sea-bottles. Imbedded in these strange groups of 

 creatures may sometimes be found specimens of 

 Mytiliineria 7iuttalUi^ Conr., the Sea-bottle Shell. 

 In shape it resembles an inflated bladder with the 

 spiral beaks at one end. The shell is very thin, 



