174 POLYTROPA. 



which was of too brisk a nature for their well-known and charac- 

 teristic slowness. When the obscuring sands which they had 

 thrown up in the fray had settled, we saw that the shells were 

 principally in possession of hermit crabs, which, under this guise, 

 were attacking a Purpura lapillus and dragging it from its shell. 

 We caught the whole school at once and transferred them to a 

 collecting-bag ; the shells occupied were Nassa pyymaea, Trochus 

 cinereus, Littorina littorea, three sizes, and a P. lapillus, the 

 sheik of the party, for lie was taken red-handed. We presume to 

 think that if their object had not been frustrated, there would 

 have been ere long a mutual exchange of crab's clothing."* 



Varieties major, minor, and imbricata are enumerated by 

 European naturalists. I give figures of the first (fig. 135), and 

 third (fig. 131), of these varieties from Forbes and Hanley. 

 besides a young shell (fig. 139) and several adults from Kiister 

 and Kiener. The variety major, of Europe is very suggestive 

 of P. crispata, of the Pacific coast of North America, and differs 

 quite as much from extreme depauperate forms as does the latter 

 ( so-called) species from P. ostrina. 





 P. saxicola, Val. PI. ^3, figs. 152-154a. 



This is normally the lapillus of the W. Coast of N. America , 

 extending from the California Islands northward to Sitka, and 

 recurring in Japan. Towards the south it becomes shorter, wider, 

 usually thinner, darker colored, tuberculate, assuming the suc- 

 cessive forms of ostrina and emarginata, whilst towards the 

 north it seems to run into lima, septentrionalis , crispata, etc. 

 generally larger, heavier, smooth or lamellate forms, with the 

 outer lip thickened and toothed internally. The type of P. 

 Freycineti, Desh. (fig. 153), is a young shell of large size, very 

 like saxicola; but there is considerable variation in the forms 

 that have been referred to Freycineti. P. ostrina, Gould (fig. 

 1544), is a small form of the saxicola type, characterized by short 

 spire, gibbous whorls, smooth or spirally ribbed, color usually 

 dark chocolate, the ribs white. P. fuscata, Forbes (fig. 

 is similar in ornamentation and color, but the spire is longer. 



* The Naturalist, 1878-79. 



