24 U.S. NATIONAL MUSEUM BULLETIN 236 



Family Acartiidae G. O. Sars, 1903 



Genus Acartia Dana, 1846 

 Acartia (Acanthacartia) tonsa Dana, 1849 



Figures lb,c 



Acartia tonsa Dana, 1849, p. 26; 1853, p. 1122; 1855, pi. 79 (fig. 4).— Giesbrecht, 

 1889, p. 25; 1892, pp. 508, 511, 518, 522, pi. 30 (figs. 7, 24, 34), pi. 43 (figs. 6, 

 10).— Dahl, 1894, p. 22.— Giesbrecht and Schmeil, 1898, p. 154.— Cleve, 

 1900, p. 44; 1900a, p. 143; 1901, p. 4; 1904, p. 355.— Foster, 1904, p. 75.— 

 Esterly, 1905, p. 204, fig. 49.— Wolfenden, 1905, p. 1023.— Sharpe, 1910, 

 pp. 407, 414, fig. 5.— Esterly, 1917, p. 393; 1919, p. 16.— Bigelow, 1922, 

 p. 146, fig. 48.— Esterly, 1923, p. 420.— Steuer, 1923, p. 23, figs. 106-109.— 

 Esterly, 1924, p. 105, figs. N, O.— Bigelow, 1926, p. 181.— Remy, 1927, 

 pp. 31, 32; 1927a, pp. 169-186, figs. 1-3.— Russell, 1927, p. 245.— Esterly, 

 1928, pp. 272, 298.— Gurney, 1931, p. 217.— C. B. Wilson, 1932, p. 160, 

 fig. 109.— Gurney, 1933, p. 373.— Rose, 1933, p. 276, fig. 348.— Steuer, 

 1933, pp. 272, 276.— Jespersen, 1934, p. 54.— Redeke, 1934, p. 39, figs. 2, 3; 

 1935, p. 315, figs. 1, 3, 5. — Fish and Johnson, 1937, p. 253.— Bigelow and 

 Sears, 1939, p. 303.— Berzins, 1940, p. 484.— Johnson, 1942, p. 28.— Davis, 

 1944, p. 3.— Vorstman, 1946, pp. 184-188, fig. 1.— Farran, 1948, p. 3, 

 fig. 6.— Sutchff, 1948, p. 234.— Jespersen, 1949, pp. 5, 8, 9.— Brodsky, 1950, 

 p. 427, fig. 302.— Davis, 1950, p. 91.— Carvalho, 1952, p. 152.— Conover, 

 1956, pp. 156-233, figs. 1-29.— Deevey, 1956, p. 127.— Maemets and Veldre, 

 1956, pp. 19, 85, pi. 10 (figs. 3-6).— Conover, 1957, pp. 65, 66.— Grice, 1960, 

 pp. 220, 221.— Stock and de Vos, 1960, p. 204. 



Material. — Loc. 194-E-5, 1 ad. 9, 0.97 mm. Loc. 592, 1 ad. cT, 

 0.93 mm. 



The area of distribution of Acartia tonsa is very extensive and in- 

 cludes tropical, subtropical, and temperate parts of the Atlantic and 

 Pacific oceans. Its pattern of distribution, which will not be given 

 in detail here, shows that the species is very tolerant in regard to the 

 temperature of surface waters in which it prefers to live. The marked 

 tendency, in the Atlantic at least, to penetrate into estuarine waters, 

 is well known, with the result that, in addition to purely marine 

 habitats, the species also has been found in Ringk0bing Fjord in 

 Denmark (Jespersen, 1934) ; the Baltic axea (Berzins, 1940; Vorstman, 

 1946); various brackish localities in the Netherlands (Kedeke, 1934, 

 1935) ; the Caen Canal in France (Remy, 1927) ; and the estuary of the 

 Amazon River in Brazil (Dahl, 1894). Its occurrence among the 

 surface lagoon plankton of Ifaluk is not surprising at all, but its 

 occm'rence at locality 592, where a sand sample was collected about 

 340 feet from the reef margin, is purely accidental; it must have been 

 washed into a small tidal pool by the flood water. 



