ALBATROSS POLYCHAETA. 



INTRODUCTION. 



The annelids with which the present memoir is concerned are embraced 

 in collections made by the Albatross during three distinct expeditmns in 

 charge of Mr. Alexander Agassiz to contiguous, and in some degree overlapping, 

 areas of the Tropical Pacific Ocean. In the first of these, explorations were 

 made off the west coasts of Mexico, Central, and northern South America, 

 and off the Galapagos Islands from February to May, 1891. So far as con- 

 cerns the polychaetes collected, the second expedition covered the region from 

 the Marquesas and Paumotus westward to the Ellice, Gilbert, and Marshall 

 Islands and was carried on from September, 1899, to March, 1900. The third 

 expedition, continued from October, 1904, to March, 1905, covered an extensive 

 area principally off the South American coast from Panama southward to 

 Peru and eastward to the Galapagos, Easter Island, and the Paumotus. In 

 addition, thirteen species from earlier expeditions of the Albatross in the 

 Atlantic are hsted in this Memoir. 



These three expeditions, with the exception in some degree of the second, 

 covered areas essentially untouched by other expeditions, and the annelid 

 forms have proved in large measure new. No fewer than one hundred and 

 eighteen out of a total of one hundred and seventy-five species seem not to 

 have been previously described, these including twenty-three new generic 

 types of which several are of high interest. While the littoral forms are well 

 represented, these coming chiefly from Panama and the Polynesian Islands, 

 chief interest attaches to the abyssal and pelagic species. The collection of 

 pelagic species is exceptionally rich and important. Aside from relatively 

 numerous representatives of strictly pelagic families, such as the Alciopidae, 

 Typhloscolecidae, and Tomopteridae, many forms from other families were 

 secured which are either in the epitokous pelagic phase or are completely pela- 

 gic. Mention may be made of the epitokes of the Nereidae, including the 



