CERATIUM SPECIES OF CARNEGIE COLLECTION 



23 



of these stations were in the region north of Samoa, and 

 it is possible that this is a region usually rich in this 

 species since one of these stations, station 159, was oc- 

 cupied seven months after the other two. 



All the records of C.bigelowii are from warm water 

 and are remote from land. The surface temperatures at 

 the stations where it was found, varied from 20.° 7 to 

 29.°4 C, except at station 57 south of Easter Island where 

 the surface temperature was 19. °0. The environmental 

 conditions in situ were: temperature, 14.°3 to 29°3 C; 

 salinity, 34.2 to 36.4 per mille; pH, 8.10 to 8.39; phos- 

 phate, 3 to 50 mg P04/m3. 



According to Nielsen's theory (1934), C. bigelowii 

 should be a shade species since it has an expanded flat- 

 tened body. Since there have been so few records of this 

 species, however, it has not been possible to examine 

 this feature heretofore. The Carnegie records in this 

 connection are not conclusive. The records of rare and 

 the total number of records for the three levels show an 

 increase In frequency with increase in depth (table 13). 

 The records of occasional, however, stand in opposition 

 to this, with the greatest frequency at 50 meters. Wheth- 

 er C. bigelowii is a shade species cannot be decided def- 

 initely imtil more records of its occurrence have been 

 accumulated. 



Since it is a large species, it was collected more 

 often in the net, with thirty-four net records, and only 

 three pump records. 



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

 samples collected at fhat depth. 



18. Ceratium inf latum (Kofoid) JOrgensen 

 Figures llO-S, chart 14, appendix table 17 



This species is very closely related to the two fol- 

 lowing. Jorgensen (1920) considered C. inf latum (Kof.) 

 Jorgensen, C. longiro strum Gourret, C. falcatum Kofoid, 

 and C. falcatiforme Jorgensen all separate species, 

 whereas Peters (1934) treated them as members of a 

 Formenkreis with subspecific rank. Nielsen (1934) con- 

 sidered them distinct. Whatever the taxonomic value of 

 these groups, there is certainly an intergradation be- 

 tween them. In this report the first three have been kept 

 separate, but this arrangement must be considered ten- 

 tative until more statistical work is done on the group. 

 It was found impossible, however, to separate C.falcati - 

 forme from C. falcatum. Therefore, only the first three 

 species are listed in this report. 



One of the characters which Jorgensen (1920) used 

 for the differentiation of the above species was length of 

 epitheca relative to length of hypotheca--the ep/hyp ratio. 

 For each species he gave the mean, minimum, and maxi- 

 mum ep/hyp ratios. It should be noted that his fractions for 

 maxima represent the maximum length of epitheca over 

 the maximum length of hypotheca and not the maximum 

 ep/hyp ratios that follow them, which might be inferred 



from his method of presentation. The same holds true 

 for his minima. Unfortunately, many of Jorgensen's fig- 

 ures for this group indicate ratios which are beyond the 

 range that he states in the text. For instance, his fig- 

 ures of C. longiro strum (figs. 26 and 27) show ep/hyp 

 ratios of 1.525 and 1.55, whereas in the description he 

 states that the ma;>Lmum ratio is 1.45. Which is correct, 

 the figures or the description? Owing to these inaccura- 

 cies it is difficult to evaluate Jorgensen's data. 



A study of the Carnegie specimens, however, re- 

 sulted in measurements showing fairly close agreement 

 with those of Jorgensen. For C. inf latum he gave an 

 ep/hyp ratio of 1.15 (1.06 to 1.26) for an a form and 1.21 

 (1.18 to 1.23) for "another form." This ratio in the 

 present material was 1.11 (0.86 to 1.25). Equally close 

 agreement was found in the case of the other species 

 (which see). The total length in our material is 1010 

 microns (640 to 1460); the diameter 40 microns (30 to 

 80). Incidentally, C. inf latum in our material is easily 

 separated from C. longirostrum bv its diameter alone, 

 since the latter has a diameter of 19 microns (15 to 27). 



It must also be noted that C. bigelowii is closely re- 

 lated to C. inf latum and should be included in the group 

 in case it is treated as a Formenkreis. In the Carnegie 

 material quite wide specimens of C. inf latum were found 

 which were difficult to separate from C. bigelowii . This 

 was particularly true where there was a lateral flatten- 

 ing of the body (fig. IIR). 



Ceratium inflatum is a rare, intolerant tropical spe- 

 cies confined entirely to warm water. In the Carnegie 

 collection it occurred at twenty-four stations- -five in the 

 Atlantic and nineteen in the Pacific. There were thirty- 

 one records of occurrence, thirty of which were rare and 

 one occasional. Twenty-five were from net samples and 

 six were from pump samples. 



The record stations for this species were scattered 

 over the warm-water regions. All of them were remote 

 from land, except one near Panama. The surf ace tempera- 

 tures at these stations were from 26.°0 to 27.°2 in the At- 

 lantic, and from 22.°3 to 28.°0C in the Pacific, except at 

 one station south of Easter Island where the temperature 

 was 19° C. The environmental conditions in situ were: 

 temperature, 16.°6 to 28.°6 C; salinity, 34.3 to 36.8 per 

 mille; pH, 8.00 to 8.37; phosphate, 3 to 121 mg P04/m3. 



Ceratium inflatum is apparently an oligotrophic spe- 

 cies. Not only was it foiud principally in warm water re- 

 mote from land, but It was usually found in water of low 

 nutrient content. More than half (seventeen) of the 

 twenty-nine records of its occurrence were in water con- 

 taining less than 10 mg P04/m3. 



Nielsen (1934) suggested that this was a surface spe- 

 cies although also found in the deeper samples. In the 

 Carnegie collection it had its maximum frequency at 50 

 meters (see table 14). Thus, the data acquired so far in- 

 dicate that the occurrence of C. inflatum is rather gener- 

 al in a vertical direction. 



Table 14. 



Records of occurrence of C. inflatum 

 at three levels 



Rare 

 Occasional 



Total 



12 







2.9 



11 

 1 



3.9 

 0.4 



2.4 



12 



2.9 



12 4.3 



2.4 



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

 samples collected at that depth. 



