24 U.S. NATIONAL MUSEUM BULLETIN 258 



body and second gnathopods is recognized herein. Because of its 

 remarkable appearance and its abundance it should be marked as 

 a distinct member of the Californian fauna, even though it is not 

 distinguished nomenclaturally. 



Geographic Relationships of Californian Amphipoda 



Eastern Pacific relationships. — More than 25 percent of the 

 Californian amphipodan fauna is of unknown geographic affinities 

 (table 30), but taxa of northern (table 28) and of southern character 

 (table 29) have been detected. The latter elements are of approxi- 

 mately equal diversity but each is less manifold than that "ubiqui- 

 tous" element (table 27) found throughout the area. Amphipodan 

 faunas to the north of California have been studied more thoroughly 

 than those to the south and this results in a stronger northern aspect 

 to the southern Californian fauna than is perhaps realistic. Probably 

 most of the species of unknown affinity (table 30) are either southern 

 in affinity or are endemic to warm-temperate waters. 



In those diverse faunas of Corona del Mar and Cayucos the most 

 frequently occurring taxa are ubiquitous in California, for example: 

 Hyale rubra jrequens, Aoroides columbiae, Jassa falcata, Ericthonius 

 brasiliensis, Microjassa litotes, Eurystheus thompsoni, Photis brevipes, 

 Parapleustes pugettensis, and Elasmopus rapax mutatus. North of Pt. 

 Conception, however, other species of northern affinity also occur in 

 abundance: Oligochinus lighti, Parapleustes nautilus, and Pontogeneia 

 rostrata. South of Pt. Conception several southern species are abun- 

 dant: Photis elephantis, Cheiriphotis megacheles, Megamphopus eflrenus, 

 M. martesia, and Microdeutopus schmitti. At impoverished sites such 

 as Pt. Dume the individuals of the northern Parallorchestes ochotensis 

 are quite abundant and at Hazard Canyon and Carmel the pre- 

 sumedly Californian Lysianassa macromerus and the northern Oligo- 

 chinus lighti are frequent in occurrence. 



About one third of the southern species is known to be tropico- 

 politan and many but not all of the remainder may be tropical pan- 

 American in distribution. 



Coincidentally, about one third of the northern species has been 

 identified in boreal seas on both sides of the Pacific Ocean, although 

 some of the identifications are questionable. 



About one quarter of the ubiquitous Californian species is also 

 extrinsic, some taxa being cosmopolitan, others of northwestern 

 Pacific affinity and one, Heterophlias, of tropical American affinity. 

 Many of the so-called ubiquitous Californian species undoubtedly 

 occur southward only to Magdalena Bay on the Baja Californian 

 coast where subtropical and warm-temperate faunas are replaced 



