LAMP-SHELLS AND THEIR ALLIES 27 



in Figure ii, as might be expected by the name, 

 but the narrow end of the shell is much shorter. 

 The specimens in my cabinet were obtained from 

 San Pedro Bay. 



At this point it may be well to explain just 

 what is meant by the locations designated as 

 "north" and ''south," also the adjectives ''northern" 

 and "southern." 



Beginning at the southwestern corner of the 

 United States, the Pacific Ocean forms the western 

 boundary of California, Oregon, Washington, Brit- 

 ish Columbia, and Alaska. At San Diego and San 

 Pedro, which lie on the coast of the southern part of 

 California, the water is nearly as warm as it is off 

 the coast of northern Mexico. Near Point Concep- 

 cion there is a decided change in the temperature, 

 and many species of mollusks which are freely found 

 farther south are seldom seen north of that angle in 

 the coast line. 



The remaining part of the coast of California, 

 together with that of Oregon and southern Washing- 

 ton, forms a "central" region; while Puget Sound 

 and the adjoining waters may be spoken of as the 

 northern region, or simply as the north. The 

 Alaskan waters are still colder, and have their own 

 inhabitants. By the "south," or "southern" Cali- 

 fornia, we refer to the coast south of Point Concep- 

 cion, and not to any specific section of the State. 

 The "north" refers to the cooler waters along the 

 coast of northern Washington and Vancouver Island, 

 while still more northern coasts are designated as 

 "Alaskan." 



