HORIZONTAL DISTRIBUTION OF CERATIUM 



C. arietinum 

 subsp. arietinum at six stations 

 subsp. bucephalum at two stations 



C. fusus 



C. pentagonvun 

 subsp. pacificum 



C. tripos 

 subsp. atlanticum at seven stations 

 subsp. semipulchellum at one station 



The following species were found at three or less 

 stations in the region. This list is composed of subpo- 

 lar, cosmopolitan, very tolerant, and slightly tolerant 

 tropical species. 



C. azoricum 

 C. carriense 

 C. contrarium 

 C. furca 

 C. horridum 



V. horridvun 

 C. massiliense 

 C. tenue 



V. inclinat\un 



C. candelabrtmi 

 C. concilians 

 C. extensum 

 C. gravidum 

 C. lineatum 

 C. macroceros 



subsp. gallicum 

 C. petersii 



Region IV. Warm Pacific (stations 45 to 47. 63 to 

 66. 78 to 115. and 129 to 160) . --This region includes 

 eighty-seven stations covering the tropical Pacific and 

 extending to approximately 40° north and 35° south lati- 

 tudes except in the southeast Pacific where it meets the 

 southeast Pacific region. Region IV is characterized by 

 warm water with surface temperatures above 20° except 

 at the borders of the region where it is lower, particu- 

 larly off California where stations with surface tempera- 

 tures as low as 16.°3 have been recorded. The phosphate 

 content of the water in this region Is not the same 

 throughout. The central part of the North pacific is 

 practically devoid of phosphate and mean values for the 

 upper 50 meters is under 10 mg P04/m3, At the north- 

 em limits of the region these values increase to 25 mg. 

 The phosphate content of the water in the southern part 

 of region IV is mostly above 25 mg except in the Easter 

 Island Eddy where it is between 10 and 25 mg. 



Region IV is characterized by a large number of 

 species of Ceratium per sta^on although the total plank- 

 ton population is low on the whole. The number of Cera- 

 tium species per station is everywhere between twenty 

 and thirty except for four stations near the equator 

 where it is over thirty and at the northern transitions 

 where it is between ten and twenty. 



The Ceratium flora of this region is distinctly tropi- 

 cal and includes all the strictly tropical species as well 

 as the tolerant ones and cosmopolitan and stray subpolar 

 forms. 



The following species were found at more than sixty 

 stations in this region. This list is composed principal- 

 ly of slightly tolerant and very tolerant tropical species. 



C. candelabrum 



C. carriense 



C. contortum 



C. contrarium 



C. declinatum 



C. euarcuatum 



C. extensum 



C. gibberum 



C. gravidum 



C. hexacanthum 



C. macroceros subsp. gallicum 



C. massiliense 



C. tenue 

 v. inclinatum at fifty -eight stations 

 V. tenuissimum at twenty-one stations 



C. tripos 

 subsp. atlanticum at twelve stations 

 subsp. semipulchellum at seventy -five stations 



The following species were found at twenty-five to 

 sixty stations in the region. This list is composedmost- 

 ly of Intolerant and slightly tolerant tropical species. 



C. arietinum 



subsp. arietinum at sixteen stations 



subsp. bucephalum at fifteen stations 

 C. bigelowii 

 C. breve 

 C. cephalotum 

 C. concilians 

 C. deflexvun 

 C. falcatum 

 C. furca 

 C. fusus 

 C. limulus 

 C. lunula 

 C. paradoxides 

 C. pentagonum 



subsp. tenerum 

 C. praelongum v 



C. platycorne 

 C. pulchellum 

 C. ranipes 

 C. subrobustimi 

 C. symmetricum 

 C. teres 

 C. vultur 



v. sumatranum at thirty-four stations 



V. regulare at one station 



V. reversum at six stations 



V. pavillardll at seven stations 



V. vultur at sixteen stations 



V. japonicum at eighteen stations 



The following species were found at less than twenty- 

 five of the stations in the region. This List, also, is com- 

 posed principally of Intolerant and slightly tolerant spe- 

 cies. 



C. arcticum v. longlpes 



C. aultii 



C. axlale 



C. azoricum 



C. belone 



C. bohmii 



C. carneglei 



C. digltatum 



C. filicorne 



C. genlculatum 



C. horridum 



V. horridum at ten stations 



v. claviger at ten stations 



V. moUe at seven stations 

 C. incisiun 

 C. inf latum 

 C. kofoidii 

 C. longirostrum 

 C. petersii 

 C. reflexum 

 C. setaceum 



Reeflon V. Southeast Pacific (stations 35, 36. 38 to 

 44. 58 to 62. and 67 to 77) .--This region includes twenty- 

 five stations in the southeastern Pacific from Panama to 

 40° south latitude and from the South American coast 



