CERATroM IN THE PACIFIC AND NORTH ATLANTIC OCEANS 



and each of these were found at only one station in the 

 southern limit of the region. 



Region 11. Warm Atlantic (stations 1 to 2. 11 to 



M- 



— This region includes twenty-three stations, all of 

 which lie south of 40° north latitude. The entire area is 

 composed of water with surface temperatures above 20° 

 C. The phosphate content is extremely low everywhere 

 except at the three northernmost stations where the 

 mean values for the upper 50 meters were from 14 to 

 52 mg POl/m^. At the rest of the stations the values 

 were 10 mg or less. Consequently, except to the north, 

 the region supports a very small quantity of plankton and 

 is distinctly oligotrophic. The sparse plankton, however, 

 is composed of a large number of species. This number 

 was between ten and twenty per station in the Caribbean 

 Sea and western part of the North Equatorial Current, 

 but higher at the other stations, being between twenty 

 and thirty species per station at all stations but station 

 16 where there were thirty-three. The total number of 

 species found in this region was forty -six. 



The Ceratium flora in region n is distinctly tropi- 

 cal, with the usual number of cosmopolitan forms and a 

 few subpolar occasionals. The following species were 

 found at fifteen or more of the twenty-three stations. 

 This lists represents only intolerant and slightly toler- 

 ant forms except for two very tolerant species (C. hexa- 

 canthum and C. massiliense) and two cosmopolitan spe- 

 cies (C. macroceros and C. tripos) . 



C. breve 

 C. candelabrum 

 C. contortum 

 C. contrarium 

 C. euarcuatum 

 C. gibber um 

 C. gravidum 

 C. hexacanthum 

 C. macroceros 



subsp. macroceros at three stations 



subsp. gallicum at twenty-one stations 

 C. massiliense 

 C. ranipes 

 C. tenue 



V. inclinatum at seventeen stations 



V. tenuissimum at seven stations 

 C. tripos 



subsp. atlanticum at eight stations 



subsp. semipulchellum at nineteen stations 

 C. vultur 



V. sumatranum at fifteen stations 



V. pavillardii at eight stations 



V. japonicum at eight stations 



V. vultur at eleven stations 



V. recurvum at ten stations 



The following species were found at from five to 

 fourteen stations. They consist of tropical and cosmo- 

 politan species as well as one subpolar. 



C. arcticum 



V. arcticum at six stations 



V. longirostrum at six stations 



V. ventricossum at one station 

 C. arietinum 



subsp. arietinum at four stations 



subsp. gracilentum at two stations 

 C. carriense 

 C. declinatum 

 C. extensum 

 C. furca 

 C. fusus 



C. horridum 



V. horridum at five stations 



v. molle at nine stations 



V. claviger at one station 

 C. limulus 

 C. lunula 

 C. paradoxides 

 C. pulchelltun 

 C. reflexum 

 C. symmetricum 



V. symmetricum at one station 



V. coarctatum at nine stations 



V. orthoceros at four stations 

 C. teres 

 C. trichoceros 



The following spec: s were found at less than five 

 stations in the region. This list comprises intolerant 

 tropical species almost exclusively. 



C. azoricum C. belone 



C. cephalotum C. concilians 



C. digitatum C. falcatum 



C. humile C. incisum 



C inf latum C. lineatvim 



C. longirostrimi C. longissimum 

 C. subrobustum 



The relative frequency of the species in this region 

 is approximately the same as that for the collection as & 

 whole so that no particular significance can be attached 

 to it. The species that are rare in region n are rare 

 throughout the world and vice versa. 



The southern part of region n corresponds to the 

 northern part of Peters' (1934) region I of the South At- 

 lantic. The composition of dominant forms in the Car - 

 negie material agrees with that of Peters. 



The area with a low n\miber of species per station 

 from stations 26 to 34, including the Caribbean Sea, can- 

 not be considered biologically different except In its 

 greater general poverty. The temperatures are higher 

 there, all above 27° or 28° C, and the plankton generally 

 sparse. Although the number of species per station is 

 generally low throughout this area, the total number for 

 the area is not, on the basis of number of stations in- 

 volved, much different from the total for region I. The 

 species not represented are mostly the rare forms. 

 Thus it is probably simply a case of a very poor produc- 

 tion of all species so that the rarer forms are seldom 

 collected. 



Region m. Cold North Pacific (stations 116 to 128) . 

 --This region includes thirteen stations, all but one of 

 which lie north of 40° north latitude. The area is com- 

 posed of cold eutrophic water with surface temperatures 

 below 17° C (as low as 7.°15 at one station), and the phos- 

 phate content of the upper 50 meters above 25 mg 

 P04/m3 at all stations but one and above 100 mg at the 

 seven northernmost stations. Consequently this region 

 supports a dense growth of plankton although the number 

 of species is small. This number is below ten at all but 

 one station. 



The Ceratium flora in this region is characterized 

 in general by a few subpolar and cosmopolitan species 

 and at the southernmost stations there are a few records 

 of slightly tolerant and very tolerant tropical species. 



The following species were foxmd at more than three 

 of the stations. They are either subpolar or cosmopoli- 

 tan species. 



C. arcticum 

 V. arcticum at two stations 

 V. longlpes at nine stations 



