HAUSTORIIDAE OF NEW ENGLAND — BOUSFIELD 163 



by the form of the fii-st gnathopods, especially in the male, and by the 

 form of the third uropods and telson. The prototype haustoriid, 

 probably not unlike Pontoporeia affinis, became specialized along two 

 main lines, stiU traceable within the Pontoporeiinae. One line, which 

 includes Amphiporeia and Bathyporeia, retained the slender body and 

 limbs and sexual dimorphism that characterize species of a non- 

 specialized feeding type and loose infaunal association. The other 

 line, leading through Pontoporeia femorata to Priscillina, evolved the 

 broadly arched body, specialized limbs, powerful pleopods, and 

 similarity of the sexes coincident with a fossorial mode of life. From 

 this second line, and probably in warm temperate regions, evolved the 

 modern haustoriinid with its unique water-pumping and filter-feeding 

 mechanism. Intermediate stages linking the pontoporeiid prototype 

 with the most primitive haustoriinid (e.g., Protohaustorius) apparently 

 did not persist to the present time. Within the Haustoriinae, the 

 form of the maxillae in Pseudohaustorius and even in Protohaustorius 

 might be interpreted as a secondary loss of the filter-feeding mechanism 

 and a return to the typical gammaridean method of feeding on large 

 food particles. 



Field behavior. — Present knowledge of the behavior and ecology 

 of the littoral haustoriids of New England is scanty. In the British 

 Isles, the feeding, swimming, and burrowing habits have been described 

 in Haustorius arenarius by Dennell (1932), in various species of Bathy- 

 poreia by Watkin (1939), and in Urothoe marina by Watkin (1940). 

 Haustorius swims on its back and burrows by a modification of the 

 swimming movements. Burrowing is dependent on the expulsive 

 action of the swimming current and cannot, therefore, be effected in 

 damp or dry sand. The filter feeding mechanism involves the collec- 

 tion of food particles via a forward-directed current in the enlarged 

 plates of maxilla II, its removal by the maxilliped setae, and sub- 

 sequent transfer to the maxilla I, mandibles, and mouth opening. 

 This mechanism is a secondary development of the raptorial feeding 

 mechanisms in normal gammaridean Amphipoda. Say's excellent 

 description (1818) of Lepidactylus dytiscus from the coast of Georgia 

 included details of swimming and burrowing behavior that clearly 

 mark the species as a member of the Haustoriinae. 



ZOOGEOGRAPHICAL AND ECOLOGICAL RELATIONSHIPS. The HaU- 



storiidae exhibit considerable ecological diversity in cool-temperate 

 regions of the northern hemisphere. Within the North Atlantic 

 region the Pontoporeiinae are best represented in the subarctic and 

 cold-temperate (boreal) regions whereas the Haustoriinae have radi- 

 ated mainly in the cool-to-warm-temperate (Virginian and Carolinian) 

 zones. The Cape Cod region of the western Atlantic occupies a 

 position of overlap between the cold-temperate faunas to the north 



