AHT. 15 COPEPOD CRUSTACEANS OF CHESAPEAKE BAY — WILSON h 



DISTRIBUTION OF SPECIES 



The distribution of the copepods in the bay may be considered 

 with reference to their geographical location, the depth and salinity 

 of the water, the time of day, the state of the tide and the kind o1 

 bottom, and the time of year when they are present in greatest abun- 

 dance. It will be found convenient to discuss these different points 

 of view under separate headings. 



GEOGRAPHIC DISTRIBUTION 



Species universally distributed. — The following 10 species (set; 

 Table 1) may be designated as universally distributed in the bay 

 Acartia clausii, A. longiremis, Centropages hamatus, C. typicub, 

 Harpacticus gracilis^ Oithona hrevicomis, O. siinilis^ Paraccdanui- 

 parvUrS, Psevdocalanus elongatus^ and Pseudodiaptomus coronatus. 



The two species of Acartia were prasent in practically every haul, 

 and numerically constituted nearly two-thirds of the entire collec- 

 tion. The two species of Centropages were absent from compar^- 

 tiveiy few hauls, chiefly at the inner end of the bay. The Harpacticuf'. 

 species was found in every part of the bay and at 23 of the 31 sta- 

 tions, but only in limited numbers. Oithona hrevicornis was nearly 

 as universal as the Acartia, occurring at every station except U, but 

 nearly always in much smaller numbers; 0. similis was present at alJ 

 the stations except four, but in even smaller numbers than brevicomiti 

 The three remaining species were found at most of the stations, but 

 seldom did they constitute more than 1 or 2 per cent of the total 

 Microthalestris littoralis was also widely distributed throughout tht 

 bay but in such small numbers and at so few (13) of the station? 

 that it can hardly be classed as universal. 



Inner-hay species. — Table 1 also shows 10 species that may bt 

 designated as belonging to the inner portion of the bay. The divi- 

 sion between the inner and outer portions falls naturally at the Mary- 

 land-Virginia State line at the mouth of the Potomac River. Thesf^ 

 species are Canuella elongata, new species, Gletodes longicaudatun, 

 Dactylopusia hrevicornis, Ectinosoma normani, Eurytemora ani-erf,' 

 cana, E. hirundoides, Harpacticus littoralis, Metacy clops graeili\, 

 Rohertsonia chesapeakensis, new species, and Tachidius littoralis. 



The new species of Canuella was obtained at Stations W and Z 

 near the extreme inner end of the bay. The Cletodes species was con- 

 fined to Station R, off Barren Island, just above the mouth of the 

 Patuxent River. Dactylopusia and Ectinosoma also occurred at sin- 

 gle stations, the former at N' and the latter at Y. The two speciej-; 

 of Eurytemora were found very sparingly in the outer bay, but quitt 

 abunJantly in the inner bay. Harpacticus littoralis was confined U 

 Stations R', S, and T. Metojcy clops gracilis appeared in a single hau i 



