CERATIUM SPECIES OF CARNEGIE COLLECTION 



27 



Pacific where the subspecies was not recorded for the 

 surface but was recorded for either or both the 50- and 

 100-meter levels. 



Table 21. Records of occurrence of C. tripos 

 subsp. semipulchellum at three levels. 



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

 samples collected at that depth. 



24. Ceratium pulchellum Schroder 



(=C. pulchellum f. eupulchellum Jorgensen) 



Figures 14B-F, chart 20, appendix table 24 



As stated above (p. 26), C. pulchellum Schroder is 

 considered distinct from the C. tripos-C. semipulcheU- 

 lum complex. It is characterized by short antapical 

 horns and small size. The diameter in our material was 

 46 (22-60) microns. 



Ceratium pulchellum is a fairly common, slightly 

 tolerant tropical species. In the Carnegie collection it 

 was found at sixty-nine stations- -eleven in the Atlantic 

 and fifty-eight in the Pacific. In the Atlantic the stations 

 were restricted to the warm Atlantic region; in the Pa- 

 cific they were scattered over the warm Pacific region 

 and the southern part of the southeast Pacific region. 

 The total number of sample records for the species was 

 158, of which 97 were rare, 47 occasional, and 14 com- 

 mon. It is a curious fact that the relative number of 

 pump records for the species is greater than the net 

 samples. The species was found in 15 per cent (82) of 

 the net samples and 21 per cent (76) of the pump sam- 

 ples. This probably is owing to the relatively small di- 

 ameter of the species and to the short antapical horns, 

 which permit the species to pass more readily through 

 the coarser cloth of the tow net. 



The surface temperatures at the stations where the 

 species was found, varied from 16.°9 (in the southeastern 

 Pacific) to 29.°5 C (north of Samoa). The environmental 

 conditions in situ were: temperature, ll.°4to 29.°4 C; 



Table 22. Records of occurrence of C. pulchellum 

 at three levels 



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

 samples collected at that depth. 



salinity, 34.0 to 37.1 per miUe; pH, 7.76 to 8.39; phos- 

 phate, 3 to 123 mg P04/m3. 



Ceratium pulchellum is decidedly a surface species 

 as can be seen from table 22. 



25. Ceratium humile Jorgensen 

 Figure 14A 



This species was reported from Japanese waters by 

 JOrgensen (1911), and from the Australian region by Niel- 

 sen (1934). The latter author considered it endemic in 

 the East-Asiatic Australian region. He also considered 

 it a purely neritic species. For this reason, the single 

 record of this species in the Carneg ie collection is re- 

 markable. 1 was foimd in the surface sample at station 

 1 in the Gulf Stream . This not only extends the known 

 distribution of the species to another ocean but indicates 

 that, at least in the Atlantic, it is not necessarily a neri- 

 tic species. The surface temperature at this station was 

 24.°0 C. The specimen (fig. 14A) resembles those figured 

 by Jorgensen (1911, figs. 82 and 83) somewhat more than 

 that figured by Nielsen (1934, fig. 34) as the right horn is 

 more ascending. 



26. Ceratium breve (Ostenfeld and Schmidt) Schroder 

 Figures 14G-P, chart 21, appendix table 25 



This is avariable species which exhibits transitions 

 to many other species of the genus, namely, C. schmidtii . 

 C. tripos , and C. arcuatum . Peters (1934) has sugge_sted 

 that it be included in the Formenkreis C. tripos . Bohm 

 stressed the similarity between C. breve and C. arcuatum 

 Cleve and the present authors believe that C. schmidtii 

 likewise is similar or identical to C. breve. A series of 

 specimens is shown in figures 14G to P which extends 

 from the form with short, curved antapicals as in C. 

 schmidtii (fig. 141) to the open parallelum type simulat- 

 ing C. arcuatum (fig. 14K). It is probable, as Bohm (1931) 

 stated, that the transition to C. arcuatum is superficial 

 rather than genetic. Whether C. schmidtii should be in- 

 cluded in C. breve is more difficult to say. According to 

 Jorgensen (1911) the body of C. schmidtii is concave so 

 the antapical horns have a ventral curvature. This fea- 

 ture, however, is sometimes found in C. breve , so it is 

 not possible to separate these two forms on that basis. 



Ceratium breve is an intolerant tropical species. In 

 the Carnegie collection it was found at ninety-two stations- - 

 eighteen in the Atlantic and seventy-four in the Pacific. 

 All the Atlantic stations were in the warm Atlantic region. 

 The Pacific stations were in the warm Pacific region or 

 the western part of the southeast Pacific region, with the 

 single exception of station 70 off Peru. The surface tem- 

 perature there, however, was high, namely, 21.°2C. The 

 species was not found in most of the southeastern Pacific 

 nor in most of the area between California and Hawaii. 

 This distribution may represent the effects of subpolar 

 currents (see p. 9). The complete range of surface tem- 

 peratures was 18.°7 to 29.°5 C. The environmental condi- 

 tions in situ were: temperature, 12^5 to 29.°4 C; salinity, 

 29.7 to 36.8 per mille; pH, 7.68 to 8.47; phosphate, 2 to 

 189 mg P04/m3. 



Melsen (1934) classified C. breve as a surface form. 

 The Carnegie data corroborate this classification. As 

 shown in table 23, it was found less frequently in the 

 deeper samples. If due correction were made for the 



