CERATIUM SPECIES OF CARNEGIE COLLECTION 



37 



the case of C. paradoxides. Of the fifty-three records, 

 only one was from the surface, whereas there were thir- 

 teen from 50 meters, and thirty-nine from 100 meters. 

 The percent.ages are even more striking (table 37). 



Table 37. Records of occurrence of C. platycorne 

 at three levels 



Rare 1 0.3 



Occasional 



Common .... ^ 



Total 1 0.3 13 4.6 39 15.4 



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

 samples collected at that depth. 



45. Ceratium ranlpes Cleve 

 Figures 19I-K, 20, 21A, chart 36, appendix table 41 



This is a rather common, slightly tolerant tropical 

 species. It is variable in respect to the number of "fin- 

 gers;" there may be three or four (fig. 21 A) or 19 and 21 

 (fig. 20). The "few-fingered" forms were formerly seg- 

 regated as var. ranipes of C.palmatum but, since a com- 

 plete intergradation between it and the main species is 

 commonly found, the variety recently has been disregard- 

 ed (Peters, 1934; Nielsen, 1934). There is a great varia- 

 tion in the length of theantapical horns. The long horns 

 usually have fewer fingers (cf. figs. 191, 21A). A specimen 

 was found in the Carnegie collection with an extremely 

 large number of fingers (fig. 20). There were nineteen on 

 the left horn and twenty-one on the right. Accordlngto the 

 theory of shade forms (Nielsen, 1934), extreme flattening 

 of the ends of the hind horns and their division into a num- 

 ber of linear branches represents an adaptation of the 

 species to shade conditions. This is substantiated by the 

 tact that the hind horns and fingers are densely packed 

 with chromatophores, and is conclusively shown by the 

 vertical distribution of species records (see below). 



The horizontal distribution of C. ranipes is typical 

 of slightly tolerant tropical species. It shows a slight 

 tendency to drift out of the tropical regions. It was found 

 at a total of seventy-nine Carne^ e stations — twenty-one 

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

 lantic the stations were all confined to the warm Atlantic 

 region, with the exception of one (station 3) where the 

 species was displaced into colder water (surface temper- 

 ature 15.°5 C). In the Pacific the stations were llmitedto 

 the warm Pacific region and the southeast Pacific region. 

 The range of surface temperatures at the Pacific record 

 staUons was 18.°7 to 29.°5 C. 



The ranges of environmental conditions in situ for 

 both oceans were as follows: temperature, 13.°1 to 29.°3 

 C; salinity, 33.7 to 36.8 permille; pH, 8.00 to 8.47; phos- 

 phate, 2 to 99 mg P04/m3. 



Ceratium ranipes probably is more or less uniform- 

 ly distributed in all tropical waters. Peters (1934) foimd 

 a slight Indication of preference for oligotrophlc water in 

 the South Atlantic, but Nielsen (1934) found the species in 

 both eutrophlc and oligotrophlc water and even in neritic 

 conditions in the South Pacific. In the Carnegie collec- 

 tion no preference for oligotrophlc water was indicated. 



Forty-seven of the 147 records of occurrence were in 

 water containing less than 10 mg P04/m3. 



Ceratium ranipes is a fairly common species, as 

 indicated by Carnegie records. There was a total of 148 

 records of occurrence, with 116 rare and 32 occasional. 

 Thirty-nine of these were pump records and 108 were net 

 records. 



Cerativmi ranipes is definitely a shade species. Niel- 

 sen (1934) found it at deeper levels except at stations rich 

 in plankton where it was found mostly above 50 meters. 

 In the Carnegie collection the species was found with in- 

 creasing frequency with increase in depth down to 100 

 meters. Expressed in percentage, the number of records 

 at 100 meters was more than twice that at the surface 

 (see table 38). 



Table 38. 



Records of occurrence of C. 

 at three levels 



ranipes 



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

 samples collected at that depth. 



46. Ceratium macroceros (Ehrenberg) Vanhoffen 

 Figures 21B-F, chart 37, appendix table 42 



Ceratium macroceros is a semicosmopolitan spe- 

 cies with a peculiar distribution. In the Atlantic there 

 are two subspecies (Jorgensen, 1911, 1920). One, com- 

 monly called the main species, is northern and extends 

 south to the Bay of Biscay and the northern parts of the 

 GuU Stream. For convenience, it is here named subsp. 

 macroceros n. subsp. The tropical form is subsp. galli- 

 cum Kofoid. Jorgensen (1920) found only subsp. gallicum 

 in the Mediterranean. Peters (1934) stated that in the 

 South Atlantic subsp. gallicum predominated everywhere 

 except in regions VI and VII (south of Africa and west- 

 ward in the general latitude of 40° south), where there 

 was a form similar to the main species of the North At- 

 lantic. Unfortunately, he did not figure this form. It may 

 be an antarctic subspecies Indicating a bipolarity in the 

 Atlantic. Nielsen (1934) foimd only subsp. gallicum in 

 the South Pacific. In the Carnegie collections in the At- 

 lantic the two subspecies characteristic of the North At- 

 lantic were found. Subspecies macroceros occurred 

 north of 40° north and at two stations south of this lati- 

 tude, stations 15 and 16. Conversely, subsp. g allicum 

 occurred principally at the tropical stations but also at 

 one station north of 40° north, station 13. The specimens 

 there, however, were not typical of the tropical subspe- 

 cies but were in the nature of intergrades. 



The northern subspecies, subsp. macroceros n. subsp., 

 differs from subsp. gallicum in its size, shape, and cur- 

 vature of antapical horns. The transdiameter of the north- 

 ern form is usually from 50 to 55 microns, whereas in 

 subsp. gallicum. it is less than 50 microns. The northern 

 form is more robust generally, and the body is somewhat 

 longer. The antapical horns in the two forms leave the 

 body at about the same angles but in subsp. gallicum they 



