30 



CERATIUM IN THE PACIFIC AND NORTH ATLANTIC OCEANS 



was found more frequently in the net samples, with 100 

 net records and 56 pump records. 



Ceratium svmmetricum is a pronounced shade spe- 

 cies. Nielsen (1934) usually found it in the samples col- 

 lected below the 50-meter level except at stations rich 

 in plankton. The Carnegie dat a indicate a much greater 

 frequency in the deeper levels (see table 26). Only 12 of 

 the 156 records, or 3.1 per cent of the surface samples, 

 were from the surface, whereas the species was found 

 in 34.0 per cent of the 100-meter samples. 



The species is quite common in oligotrophic water. 

 Sixty -five of the 156 records of occur rence were in water 

 containing less than 10 mg P04/m3. The environmental 

 conditions in situ were: temperature, 12.°1 to 29.°3 C; 

 salinity, 30.7 to 37.1 per mille; pH, 7.90 to 8.39; phos- 

 phate, 3 to 152 mg P04/m3. 



31. Ceratiimi axlale Kofoid 

 Figures 15D and E, chart 25, appendix table 29 



This is a very rare intolerant tropical species. It 

 was found only twice in the collections of the Meteor in 

 the South AUantic (Peters, 1934). Nielsen (1934) found 

 it at nine stations in the Pacific in the South Equatorial 

 and East Australian currents. The Carnegie collections 

 extend the known range of the species both in the North- 

 ern and Southern hemispheres of the Pacific. It was not 

 found in the Atlantic. It occurred at eleven Carnegie sta- 

 tions; two of these were in the southeastern Pacific, one 

 off Japan, and the rest in the North Equatorial Current 

 and north and east of Hawaii. It is probable that the 

 species is more or less evenly distributed over the warm 

 waters of the world but it is seldom collected because of 

 its sparse numbers. In the Carnegie collection there 

 were thirteen records of occurrence, of which eight were 

 rare, three occasional, and two common. 



The surface temperatures at the stations where it 

 occurred, varied from 20.°2 to 28.°1 C. The ranges of en- 

 vironmental conditions in situ were: temperature, 15.°6 

 to 27.°6 C; salinity, 34.5 to 35.1 per mille; pH, 8.08 to 

 8.39; phosphate, 4 to 32 mg P04/m3. 



Five of the thirteen records were in water contain- 

 ing less than 10 mg P04/m3. 



All of Nielsen's (1934) records were from below 50- 

 meter depths except one. The Carnegie data are in good 

 agreement with his (see table 27). There was only one 

 record from a surface sample and one from a 50-meter 

 sample. The other eleven were from 100-meter sam- 

 ples. It is thus evident that C. axiale is unquestionably 

 a shade species. 



It is also of interest to note that eight of the records 

 were from pump samples, whereas only five were from 



Table 27. 



Records of occurrence of C. axiale 

 at three levels 



A=Number of records. B=Per cent of total number of 

 samples collected at that depth. 



the net samples. Apparently the curved nature of the 

 antapical horns permits the specimens to pass through 

 the coarser nets. 



32. Ceratiimi aultii n. sp. 

 Figures 15F and G 



Diameter, 55 microns; total length, 230 to 250 mi- 

 crons. The shape of the body is similar to those of C^ 

 svmmetricum and C. axiale . except that the apical horn 

 is displaced to the left. Curvatures of antapical horns 

 resemble those of C. axiale except at the bases where 

 the antapicals extend laterally from the body before they 

 curve anteriorly. 



Ceratium aultii was found at only two stations — one 

 off Peru (station 72) and the other in the central part of 

 the North Equatorial Current of the Pacific (station 151). 

 It was found at 100 meters at both stations. At station 

 72 it was "common" in the net sample; at station 151 it 

 was "rare" in the pump sample. The surface tempera- 

 tures at the stations where it was found were 24.°9 and 

 26.°0 C. The temperatures in situ were: 14.°8 at station 

 72, and 12.°5 C at station 151. 



33. Ceratium azoricum Cleve 

 Figures 16M-P, chart 26, appendix table 30 



This species is a variable and little-known form. It 

 is probably much more common than the number of rec- 

 ords for it would indicate, since it is lost through the net 

 because of its small size. It varies greatly in size (di- 

 ameter from 38 to 50 microns), however, as well as in 

 shape of body, and origin of antapical horns. The larger 

 forms with spreading horns bear a close resemblance to 

 C. peter sii and may, in fact, be identical with this, i.e., 

 C. peter sii may represent simply one end of a line of 

 variations of C. azoricum . At the other end of this line 

 are the small specimens with horns close to the body. 

 In the Carnegie collection a specimen was found which 

 had a heavy list which joined the apical with the antapical 

 horns (fig. 16M). This may be a new species as no defi- 

 nite intergrades were found between it and C. azoricxmi . 

 Since only the one specimen was found, however, it was 

 decided to postpone naming a new species until more 

 material could be examined. 



Ceratium azoricum is a very tolerant tropical spe- 

 cies. Lebour (1925) stated that it is subtropical and is 

 occasionally brought into the northern seas. In the Car- 

 negie collection it was found in the region of Ireland and 

 between Iceland and the Faeroes. In the latter region the 

 surface temperature was 8.°9 C. In the Pacific it was 

 found at one station in the cold North Pacific region, 

 where the surface temperature was 13.°3 C. In the south- 

 eastern Pacific it was found at temperatures as low as 

 16.°3 C. On the other hand, it occurred at temperatures 

 as high as 29.° 5 C in the equatorial regions. It was foimd 

 at a total of five stations in the Atlantic, only one of which 

 was in the warm Atlantic region. In the Pacific it was 

 found at twenty-three stations: one in the cold North Pa- 

 cific region, seven in the southeast- Pacific region, and 

 fifteen in the warm Pacific region. The total number of 

 records was sixty, of which thirty-eight were rare, twenty- 

 one occasional, and one common. As stated above, the 

 species is probably commoner than the reported records 

 would indicate because it probably escapes through the 



