22 



CERATIUM IN THE PACIFIC AND NORTH ATLANTIC OCEANS 



13. Ceratium bohmii n. sp. 

 Figure 12, appendix table 13 



Dimensions: diameter, d, 20.5 (18-24) microns. 



This species is closely related to C. kofoidii with 

 which Bohm (1931, figs.9C, E, and F) confused it. The 

 dimensions are about the same. The body, however, is 

 much more elongated and the horns, particularly the 

 antapicals, are much longer. The length of the hypothe- 

 ca from the base of the right antapical horn to the pos- 

 terior edge of the girdle is more than 0.5 d, whereas in 

 C. kofoidii this length is less than 0.5 d. The right ant- 

 apical diverges laterally only slightly or not at all. 



Ceratium bohmii is a tropical Pacific species, prob- 

 ably slightly tolerant, although this cannot be determined 

 at present because of the paucity of records for the spe- 

 cies. It was found at six stations widely scattered as 

 follows: two between Ecuador and the Galapagos, two 

 north of the Phoenix Islands, and two off Japan. There 

 were twelve records of occurrence — eight rare and four 

 occasional. The species was collected more frequently 

 with the pump, probably because of its small size. 

 There were three net records and nine pump records. 



The surface temperatures at the stations where the 

 species was found, varied from 18.°7 to 27.°9 C. The en- 

 vironmental conditions in situ were: temperature, 13.°9 

 to 27.°9 C; salinity, 33.7 to 35.3 per mille; pH, 7.85 to 

 8.22; phosphate, 4 to 161 mg P04/m3. 



Ceratium bohmii is probably a surface species, al- 

 though there are not sufficient records to establish this. 

 Five of the records were from surface samples, three 

 were from 50-meter samples, and four from 100-meter 

 samples. 



14. Ceratium lineatimi (Ehrenberg) Cleve 

 Figures llE-G, chart 12, appendix table 14 



Ceratium lineatum is a rare species which is diffi- 

 cult to classify geographically. It occurs in the cold 

 North Atlantic region and at three stations in the warm 

 Atlantic (chart 12). In the Pacific it occurred only off 

 Japan (stations 115a to 117). It is possibly a subpolar 

 species. Peters (1934) found it in the South Atlantic, 

 mostly in the cooler waters. At Carnegie Atlantic sta- 

 tions the species was found mostly in colder waters with 

 surface temperatures from 10.°9 to 15.°5 C except at sta- 

 tions 17 and 19. At the Pacific record stations the sur- 

 face temperatures varied from 15.°9 to 16.°1 C. The 

 environmental conditions in situ were: temperature, 6.° 7 

 to 21.°2 C; salinity: 33.8 to 37.0 per miUe; pH, 7.98 to 

 8.34; phosphate, 3 to 99 mg P04/m3. 



The total number of station records was ten, of which 

 seven were in the Atlantic and three in the Pacific. There 

 were twenty-six records of occurrence, ten of which were 

 rare, fourteen occasional, and two common. The records 

 of common were from off Japan. Twenty-one of the rec- 

 ords were from net samples and five were from pump 

 samples. The species was found frequently at the sur- 

 face, with thirteen records for the surface, six records 

 for 50 meters, and seven recrods for 100 meters. 



The authors were unable to separate C . minutum Jor- 

 gensen from C. lineatum. Jorgensen (1920) distinguished 

 C. minutum from C. lineatum by its smaller dimensions, 

 less robust theca, comparatively shorter and broader body, 

 shorter antapical horns, and relatively shorter right ant- 

 apical horn. Carnegie specimens with the shape of C. minu- 



tum have relatively thick walls (fig. IIF); specimens with 

 the typical shape of C. lineatum are in the size range of C. 

 minutum . i.e., transdiameter 25 to 28 microns (figs. HE, G). 



15. Ceratium setaceum JOrgensen 

 Figure HA, appendix table 15 



This is a very rare, slightly tolerant tropical spe- 

 cies. Nielsen (1934), who first reported it from the Pa- 

 cific, found it at only two stations- -one north of Samoa, 

 and the other west of New Zealand. In the Carnegie col- 

 lection it was found at only two stations also --station 70, 

 off Peru, and station 110, between Guam and Japan. Judg- 

 ing from the scattered nature of these records, it is 

 probable that C. setaceum is a widespread tropical spe- 

 cies, but occurs in such sparse numbers that it is seldom 

 collected. Another reason for its reported scarcity is 

 undoubtedly its small size which enables it to pass 

 through many nets. This is demonstrated by the fact that 

 all the Carnegie records were from the pump samples 

 which were collected by a much finer (no. 20) cloth than 

 the tow nets. The records were at and 50 meters at 

 station 70, and 100 meters at station 110. 



The surface temperatures at the above two stations 

 were 21. °2 and 23.°9 C. The ranges of environmental con- 

 ditions in situ were: temperature, 15.°4 to 21. °2 C; salin- 

 ity, 34.7 to 35.1 per mille; pH, 7.88 to 8.14; phosphate, 

 11 to 178 mg P04/m3. 



Subgenus AMPHICERATIUM 



16. Ceratium geniculatum (Lemmermann) Cleve 

 Figure 11 J 



This is a very rare tropical species. Only one spec- 

 imen was found in the Carnegie collection, and this was 

 partially broken (fig. IIJ). It occurred in the 50 -meter 

 pump sample at station 45, latitude 4.°5 south, longitude 

 105° west. The temperature was 22.°4 C; salinity, 35.2 

 per mille; pH, 8.13; and phosphate 46 mg P04/m*. 



17. Ceratium bigelowii Kofoid 

 Figures 11 1, K-M, chart 13, appendix table 16 



This is a very rare intolerant tropical species, ap- 

 parently confined to the Pacific and Indian oceans. It has 

 never been reported from the Atlantic. It was reported 

 from the Pacific by Kofoid (1907a) and Nielsen (1934), 

 and from the Pacific and Vidian oceans by BOhm (1931). 

 Nielsen foimd it at four stations in the South Equatorial 

 Current. The Carnegie records contribute considerably 

 to our knowledge of the distribution of this species in the 

 Pacific. They show that it is not restricted to any par- 

 ticular current system, but is distributed over the warm 

 tropical waters in both hemispheres. &i the Carnegie 

 collection it was found at twenty-four stations (chart 13). 

 These are distributed in the southeastern Pacific to lati- 

 tude 34° south (station 57), in the northwestern Pacific to 

 latitude 23.°5 north, and in the northeastern Pacific to 

 26° north latitude. There are forty records of occur- 

 rence --thirty- six rare and four occasional. The records 

 of occasional were at 50 meters at stations 95, 96, and 

 159, and also at the surface at the last station. All three 



