BIGELOW: EXPLORATIONS OF THE COAST WATERS. 245 



the latter (Euthemisto) composed the bulk of the plankton (Fig. 79) 

 in the waters along the outer edge of the shelf off Marthas Vineyard, 

 on the outer part of Georges Bank and off Halifax ; while euphausiids 

 played a similar role on Brown's Bank, (Station 10228) and over the 

 slope south of Shelburne (Station 10233). 



Previous experience (1915) leads us to expect Gulf Stream tempera- 

 tures and at least a large admixture of Gulf Stream fauna over the 

 continental slope all the way from Chesapeake Bay to Cape Cod; 

 and 191-i was no exception to this general rule. Thus, we encountered 

 a tropical plankton assemblage over the slope oif the west end of 

 Georges Bank (Station 10218), including the fishes Leptocephalus 

 and ]Myctophum ; Salpa fnsifornis and Doliolum ; the tropical amphi- 

 pods Phronima, Vibilia and Oxycephalus: the copepods Rhincalanus 

 and Sapphirina: Sagiita enflata, S. hexaptera and Pterosagitta draco 

 (p. 294); eleven species of tropical pteropods (p. 302) and nineteen 

 species of tropical Medusae and Siphonophores, (p. 306); likewise 

 Gulf weed (Sargassum), floating on the surface. And Doliolum, 

 Phronima, a phyllosome larva and a tropical pteropod (p. 302) oc- 

 curred in the otherwise typically boreal plankton on the edge of 

 Georges Bank near Station 10219. 



At the same relative position on the slope, 100 miles further 

 east (Station 10220) the rather scanty catches were almost evenly 

 divided between boreal organisms, (e. g., Euthemistio, Aglantha, 

 Limacina halea) and animals of Gulf Stream origin (Euphausia, Nema- 

 toscelis, Rhincalanus, a phyllosome larva, Phronima, Doliolum) while 

 tlais Station was further noteworthy for the occurrence of several 

 specimens of Diphyes arciica (p. 306), which likewise occurred over the 

 slope off Shelburne in June, 1915.^ The plankton over the slope off 

 IMarthas Vineyard, in August (Station 10260, 10261) was similarly 

 divided between boreal and tropical organisms, the hauls consisting 

 chiefly of Euthemisto, with occasional Limacina balca, side by side 

 with such warm water forms as Myctophum, Phronima, and Sagitta 

 enflata. But at the same relative position on the slope off Shelburne 

 (Station 10233) the plankton was chiefly boreal, c. g., Sagitta clegans, 

 Euthemisto, Clione, Calanns finmarchicus, C. hypcrhoreus, Euchaeta, 

 Limacina balea, and Aglantha, as might be expected from the hydro- 

 graphy (p. 177), with only a minor tropical element (the copepod 

 Rhincalanus in 1914; Sagitta enflata and the fishes Cyclothone and 

 Valencienellus in June, 1915). 



I The geographical relations of D. arciica are discussed (p. 306). 



