8 PROCEEDINGS OF THE NATIONAL MUSEUM vol.80 



at Station Z, the new species of Rohertsoriia in a single haul at Sta- 

 tion T, and Tachidius littoralis in single hauls at Stations L' and W. 



Outer-hay species. — In contrast with the littoral species just 

 enunrierated, 16 others may be regarded as belonging to the outer 

 portion of the bay. These are Alteutha depressa^ Calcmus fm- 

 marchictcs, Cori/cella carinata, Gorycaeus elongatus, C. venustus^ 

 Gryptopontius gracilis, Diosaccus tenuicomis, Ha/rpacticus chelifer^ 

 Ldbidocera wollastoni^ Microsettella norvegica^ Oithona spinirost'riSy 

 Oncaea minuta, Pontella meadii, Temora longicomis, T. turhinata, 

 and Tishe furcata. 



Eight of these species were confined to single hauls at different 

 stations, two appeared at two stations each, and three at four sta- 

 tions each. Of the remaining species, Gdlanus occurred fairly abund- 

 antly in the wider portion of the bay below the mouth of the Potomac 

 River. The first species of Temora was found at the three stations 

 in the mouth of the bay and also at Station Y near the extreme 

 inner end of the bay. The other species, Temora turhinata^ was 

 most abundant at the mouth of the bay and only went up as far as 

 the mouth of the Rappahannock River. 



The parasitic species, Bomolochus e?ninens, was found in the adult 

 stage only at Station P in the inner bay, but development stages were 

 very common at nearly every station in the outer bay. The geo- 

 graphic location of these parasites, however, is determined by the 

 distribution of their hosts rather than by any locality where they 

 happen to be captured swimming freely in the tow. 



Oceanic species. — A fourth division would include such species as 

 were not found at any of the stations within the limits of the bay, 

 but were present more or less abundantly in the outside ocean. 

 There are 19 such species, and they will be found discussed on 

 page 16 under the trip to the 100-fathom line. 



SALINITY DISTKIBUnON 



The salinity records made during the investigation vary all the 

 way from 31.74 per cent on the bottom at Station G in the mouth 

 of the bay down to 4.75 on the surface at Station U, the innermost 

 station opposite the mouth of the Patapsco River. If we recall, in 

 connection with this remarkable range in salinity, what has already 

 been said with regard to the kaleidoscopic changes produced by the 

 tides and the seasons, certain deductions naturally follow : 



1. The 10 species universally distributed, especially the two 

 Acartias and Earpacticus gracilis., must be able to accommodate 

 themselves to great and fairly rapid changes in salinity. The three 

 species mentioned were taken in surface hauls at Stations G and U, 

 and the two Acartias also appeared in the bottom hauls. The depth 



