232 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



series of observations has been made on tlie area northeast of a line drawn from 

 San Francisco to Uualashka Island. Tlie chief oceanic current in this area is tiie 

 enfeebled remnant of the Kuro Siwo and its deflected northerly and southerly 

 arms. A drift of Arctic water southward is noticeable near the passes between 

 the Aleutian Islands. The latter brings Clione and Limacina from Bering Sea, 

 and the latter genus reaches, on the southerly arm, or coastal current, sometimes 

 as far south as Monterey, California. 



The Kuro Siwo is at the height of its strength and temperature in the early part 

 of September in this region. Its surface water 300 miles off shore sometimes 

 rises as high as 68° Fahrenheit, though the heat is rapidly given off to the atmos- 

 phere after the coast is reached, and the southerly arm off San Francisco has a tem- 

 perature of only 54° Fahrenheit. The warm belt is never more than fifty miles 

 in width in the area in question. The current is imperceptible, as such, in winter 

 and early spring, when one encounters only northern pteropods. At this season, 

 and well up to July, no pteropods of the genera Cleodora, Cavolina, Pueuinoder- 

 mon, and Corolla were taken north of latitude 38°. After this time the Kuro 

 Siwo water begins to be noticed in the temperatures, and the forms mentioned are 

 more or less prevalent in small swarms. In September they exist in great abun- 

 dance, brought in the warm water as far north as latitude 50° and less abundantly 

 to latitude 54°. 



Tlie Cavolina, Cleodora, and Pneumodermon are apt to appear (when present 

 in the area) at the surface during calms, especially if the sun be overcast. The 

 last mentioned genus is particularly noticeable from the disturbance caused by 

 the rapid movements of its large and powerful flippers. Its motions recall those 

 of humblebees over a field of clover. If a breeze of any strength springs up, the 

 pteropods sink to a calmer stratum. I am unable to say positively that they are 

 habitually crepuscular, but it is a fact that my largest hauls have been made 

 about sundown. These animals are not equally distributed over the sea, but are 

 distinctly gregarious, occurring in large swarms, which are trailed out into long 

 bauds by the action of the winds. Adjacent tracts of ocean may be almost desti- 

 tute of pteropods. I was much surprised in opening the stomach of a large 

 sunfish taken off Point Reyes, California, to find it crammed with Cleodora. That 

 such a slow and clumsy creature as Orthugoriscus mola could gorge itself with 

 the nimble pteropods was indeed remarkable. Another fact of interest was 

 developed by the examination of molluscan fragments found in the stomachs of 

 the Pacific salmon fresh from the sea, sent me by Professor Kofoid of the Uni- 

 versity of California for identification. These consisted almost exclusively of 

 Spirialis and Limacina, showing that the last meal of the fish had been taken in 

 cold water. In the Northeast Pacific 1 have not taken these two genera in the 

 open sea, but only near shore in the colder coast currents. 



The form collected by me in 18G5 and 1871, and from living specimens of 

 whicli carefully enlarged colored figures were drawn, difl"ercd so much from the 

 figures given by Rang, Souleyct, and otlier authors as representing the Mediter- 

 ranean iridentata (= fclemu^) that it seemed impossible that both should belong 



