CERATIUM SPECIES OF CARNEGIE COLLECTION 



45 



species. He found tiiat in the eastern part of the South 

 Pacific, where there were stations rich in plankton, the 

 species had its main distribution above 50 meters; at 

 the western stations, where the plankton population was 

 less dense, the species had its main distribution below 

 50 meters. The Carnegie data do not, however, substan- 

 tiate these results. The number of records in the Car- 

 negie collection decreased with increase in depth. Per- 

 haps, if a classification of the Carnegie tropical stations 

 as to plankton content could be made, some correlation 

 with plankton density could be discovered. The authors 

 can conclude that C. hexacanthum . however, is not a 

 typical shade species as many other species in the Car- 

 negie collection showed a decided increase in frequency 

 of occurrence with increase in depth, considering the 

 collection as a whole. 



Table 50. 



Records of occurrence of C. 

 at three levels 



hexacanthum 



Rare 



Occasional 



Common 



Total 



72 

 63 

 13 



18.2 



16.3 



3.4 



53 



43 



9 



17.9 



15.2 



3.2 



44 17.3 



?3 9.1 



7 2.7 



148 



37.9 105 36.3 74 



29.1 



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

 samples collected at that depth. 



58. Ceratlum reflexum Cleve 

 Figure 27, chart 49, appendix table 54 



This is a very rare, intolerant tropical species. It 

 was not reported from the South Atlantic by Peters (1934) 

 although it had been reported from as far south as 19.°5 



south latitude in the Atlantic by Cleve (1900). Nielsen 

 (1934) found it at only four stations in the South Pacific. 

 In the Carnegie collection it occurred at twenty-one 

 stations--six in the Atlantic and fifteen in the Pacific. 

 The Atlantic stations were between 11° and 24° north 

 latitude. The Pacific stations were much scattered (see 

 chart 49). The range of surface temperatures at the rec- 

 ord stations for the species was from 23.°4 to 29.°4 C. 

 The ranges of environmental conditions in situ were: 

 temperature, 17.°5 to 28.°6 C; salinity, 34.4 to 37.1 per 

 mille; pH, 7.99 to 8.39; phosphate, 3 to 123mgP04/m3. 



The total number of sample records was thirty-nine, 

 of which thirty -three were rare, five occasional, and one 

 common. The record of common was at station 105 near 

 Guam; the occasional records were from station 20 (trop- 

 ical Atlantic), station 97 (near the Phoenix Islands), and 

 station 107 (near Guam). The species perhaps prefers 

 oligotrophic water since twenty -three of the thirty -nine 

 records were in water containing less than 10mgPO4/m3. 

 ^ It Is probably a shade species. Practically all Niel- 

 son's (1934) records were from the deeper layers. The 

 Carnegie data show an increase in frequency with in- 

 crease in depth (table 51). 



Table 51. 



Records of occurrence of C. reflexum 

 at three levels 



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

 samples collected at that depth. 



