86 New York State Museum 



the North Pacific coast, and yet they may be readily recog- 

 nized as members of the same family. On the rocks of 

 our northern shores Periwinkles (Littorind) , Rock Pur- 

 ples, Rock Snails or Dog Whelks (Purpura) and Lim- 

 pets (Acmaea) are very abundant, and near low-water 

 mark under ledges Chitons are found; in similar places 

 on the coast of California occur the Abalone (Haliotis), 

 Acmaea and Chitons. 



Temperature is a great factor in determining the dis- 

 tribution of marine life. In recognition of climatic in- 

 fluences upon the fauna and flora of the sea, certain 

 geographical divisions of the coasts of North America 

 have been recognized. On the Atlantic coast we have the 

 boreal fauna .from Cape Cod northward, the American 

 fauna from Cape Cod to Cape Hatteras and the West 

 Indian fauna from Cape Hatteras southward. The 

 Pacific coast has similar divisions but without definite 

 names. The geographical boundaries are not hard and 

 fast. Some of the animals of one division pass over into 

 the others. Many forms that normally live far out at 

 sea drift by accident along the coast. Such are the strik- 

 ing Portuguese Man-of-War, the beautiful Purple Float- 

 ing Snail (Janthina fragilis), and hosts of jellyfishes and 

 crustaceans. The great ocean currents bring vast num- 

 bers of floating creatures from the tropics and also the 

 arctic regions far into the temperate regions. During 

 the winter and spring arctic animals live along our 

 shores, while tropical and subtropical forms occur there 

 in the summer season and early autumn. During the 

 summer months animals whose home is normally in the 

 West Indies or the Bahamas are carried by the southerly 

 winds to the southern coast of Long Island; during the 

 colder months, from November to April, under the effects 



