CERATIUM SPECIES OF CARNEGIE COLLECTION 



43 



its entire range show an increase in frequency with an 

 increase in depth (table 46). 



54. Ceratium tenue Ostenfeld and Schmidt 

 Figures 26C-D, chart 45, appendix table 50 



Two varieties of this species can be recognized: 

 var. Inclinatum . in which the antapical horns are direct- 

 ed more or less apically (fig. 26C); and var. tenuissi- 

 mum . in which the antapical horns are directed laterally 

 (fig. 26D). It is important to note that the origin and 

 proximal curvatures of the antapicals in these varieties 

 are the same, the differences being due to ciu"vatures 

 more than one-half girdle diameter from the body. 



The two varieties do not have separate ranges of 

 distribution but are found together in the warm regions 

 of the world. The species as a whole is more common 

 than C. horridura . but does not have any cold-water rep- 

 resentative. 



Peters (1934) apparently included this form in C. 

 horridum . following Jorgensen (1920), but he gave no fig- 

 ures. Nielsen (1934), who separated it from C. horridxun . 

 stated that it had a distribution in the South Pacific sim- 

 ilar to that species. 



The total number of station records for the species 

 in the Carneple collection was 100--19 of these were in 

 the Atlantic and 81 were in the Pacific. The Atlantic 

 records were all restricted to the warm Atlantic region, 

 with surface temperatures from 21. °2 to 28.°5 C. The 

 Pacific stations were in the warm Pacific region and the 

 southeast Pacific region, except for one station off Cali- 

 fornia which extended Into the cold Pacific region (sta- 

 tion 128, surface temperature 16.°4 C). Throughout its 

 range the species was found fairly uniformly except off 

 Peru and the Panama and Galapagos areas, where it sel- 

 dom occurred. 



The total number of sample records for the species 

 was 236, of which 129 were rare, 99 occasional, and 8 

 common. The net records numbered 115; the pump rec- 

 ords, 121. The environmental conditions in situ were as 

 follows: temperature, 8°8 to (29.°4) C; salinity, 33.2 to 

 37.1 per mllle; pH, 7.93 to 8.39; phosphate, 2 to 176 mg 

 P04/m3. 



Ceratium tenue Is definitely a shade species. In the 

 Carnegie collection it was foimd with increasing frequen- 

 cy with increase in depth. There were almost four times 

 as many records for 100 meters as for the surface (table 

 47). Nielsen (1934) also foimd the species to be a shade 

 form in the Pacific. 



Table 47. 



Records of occurrence of C. tenue 

 at three levels 



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

 samples collected at that depth. 



55. Ceratium longissimum (Schroder) Kofoid 

 Figures 26A-B, chart 46, appendix table 51 



This is a rare intolerant tropical species. It is not 

 variable in form and for this reason it is interesting to 

 note a constant difference in the spread of the horns be- 

 tween the Atlantic and Pacific specimens. In the Atlantic 

 form (fig. 26A) the three horns are practically parallel, 

 whereas in the Pacific form (fig. 26B) the antapicals, al- 

 though proximally almost parallel in position, soon di- 

 verge considerably from the apical horn. Also, the horns 

 In the Pacific form are much more slender. 



The species was found at twenty-eight stations- -five 

 in the Atlantic and twenty-three in the Pacific. The At- 

 lantic stations were all In the warm Atlantic region, with 

 surface temperatures above 20° C. The Pacific stations 

 were in the warm Pacific and southeast Pacific regions 

 with siu-face temperatures above 21° C. There was a 

 particular concentration of stations in the general area 

 between Hawaii and North America. The distribution as 

 a whole was closely restricted as to latitude, lying be- 

 tween latitudes 14° south and 34° north. Nielsen's (1934) 

 records, which were the first for the Pacific, lie within 

 these limits except for one station In Australian waters 

 at latitude 32° south. The temperature there, however, 

 was above 20° C. In the Atlantic the northern limit was 

 somewhat farther north than in the Pacific, namely, 38.°5 

 north. 



The rarity of the species is further shown by the 

 nimiber of sample records, which was thirty-two. Of 

 these, twenty-five were rare and seven occasional. Only 

 six were pimip records; twenty-six were net records. 

 The species may prefer oligotrophlc water as it was sel- 

 dom found in regions rich in plankton and fifteen of the 

 thirty-two records of occurrence were in water contain- 

 ing less than 10 mg P04/m3. The ranges of environmen- 

 tal conditions in situ were: temperature, 12.°3 to 28f0 C; 

 salinity, 34.3 to 36.4 per mllle; pH, 7.92 to 8.39; phos- 

 phate, 3 to 138 mg P04/m3. 



Ceratium longissimum is one of the most pronounced 

 shade species encountered. Of the thirty-two records of 

 occurrence, none were for the surface, only five for 50 

 meters, and twenty-seven for 100 meters 'see table 48). 

 Nielsen (1934) found it only in the samples taken from 200 

 to 100 meters and 100 to 50 meters. 



Table 48. Records of occurrence of C. longissimum 

 at three levels 



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

 samples collected at that depth. 



56. Ceratium arctlcum (Ehrenberg) Cleve 

 Figures 26E-H, 27A-E, chart 47, appendix table 52 



Ceratium longloes (Bailey) Gran and C. arctlcum 

 (Ehr.) Cleve Intergrade in such a way that the authors are 

 forced to include them under a single species. According 



