248 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



cincta, Ototyphlonemertes spiralis, Amphiporus peruvianus, and Tetra- 

 stemma sexlineatum, bringing the number of species found on the Pacific 

 coast of North, Central, and South America between the Arctic Ocean 

 and Ecuador to a total of 94. Two of these are bathypelagic. Several new 

 color varieties are also described. 



Of the 98 species included in this report, 4 are not known to occur 

 north of Peru and 8 others, including one bathypelagic species, have been 

 found only in the region from Ecuador to the Gulf of California. The 

 remaining 86 species, including one that is bathypelagic and one that is 

 limited to fresh water, have been reported at various localities from the 

 coast of California and northward. An appended list includes 17 supposed 

 species reported from Peru and southward which were not represented in 

 the Allan Hancock collections and which appear to differ from those 

 found on the Pacific Coast north of the equator. 



The geographical distribution as far as at present known of the 111 

 littoral species recorded from the entire coast from the Arctic Ocean to 

 Patagonia is shown in Table 1. It will be noted that 18 of the species are 

 thought to be identical with well-known European species; 17 of the 

 Pacific Coast species occur also on the Atlantic coasts south of Europe 

 and 13 on the east coast of North America. Some of them appear to have 

 a world-wide distribution. 



The changes in nomenclature and more particularly the greater 

 variability which has been found in the appearance and coloration of 

 younger and older individuals of the various species have necessitated the 

 formulation of revised keys to the families, genera, and species. 



Since the ecological conditions on the Pacific coast change gradually 

 and without well-marked faunistic barriers from the Bering Strait to 

 the equatorial regions, there is a constant overlapping in the geographical 

 distribution of the various representatives of the nemertean fauna. For 

 convenience, however, the 10,000 or more miles of seacoast comprising 

 the entire region may be considered as representing 5 intergrading zones. 

 In such a classification, the northern zone would extend from the Aleu- 

 tian Islands to the Arctic Ocean; the north central zone would include 

 the coasts of Alaska and British Columbia from the Aleutian Islands 

 to Puget Sound ; the central zone would then extend from Cape Flattery 

 to Cape Arguelos or Point Conception ; the south central, or semitropical, 

 zone would cover the coast of southern California and Lower California 

 to Cape San Lucas ; and the southern, or tropical, zone the Gulf of Cali- 

 fornia and the entire coast southward to Ecuador. 



