1869.] Contribution to our knowledge of Pelagic Ilollusca. 261 



The points of interest in the above entry are threefold : — 

 First, — the capture of H. tridentala {II. Forshthlii of D'Orb.) at 

 noon- day, D'Orbiguy having recorded it as nocturnal in its habits. 



Second, — the appearance in scores of Balantium australe. As Cape 

 Horn is its recognized habitat, its presence so far to the eastward was 

 interesting. The Salpian mass in which these animals were imbed- 

 ded was nearly a foot deep in the bottom of the net. 



Third, — that which relates to the red Untomostraca : but, as they 

 form a group in a separate class, I will merely say here, that this was 

 the second time they had disappeared suddenly at the same hour, viz. 

 when night was closing in. On each occasion, they were followed by 

 small Salpce with yellow nuclei, probably immature forms of S. maxi- 

 ma within whose organisms, however, there w r as no appearance of 

 Entomostraca. 



1868, June 25, The net was over from 6 till 10 p. m. At 



N. Lat. 5° 42', 7.30 p. m. took a solitary specimen of 



W. Long. 22° 42', Cleodora pyramidata. During the middle 

 Therm. 79°, watch from 12 to 4 A. M. the Captain's net 



Sea, 81°, was in use, and brought up numbers of Ptero- 



Strong current to pods and other marine animals. 



N. E. The next evening the net was again over 



from 6 to 10.30 p. m. and nothing wdiatever 

 came up, but three fragmentary Diphyzooids. Thus on two successive 

 occasions from sunset until 10 p. m., no living thing, except those 

 above named, was brought up, yet during the middle of the night 

 large hauls were made. Within equatorial limits, however, I have 

 generally found the middle watch to be the best time. 



The vessel here was in the neighbourhood of strong currents, and 

 they are as we know the consequence of a disturbance in the aqueous 

 equilibrium caused by a high temperature and great evaporating 

 force.* Can it be that in these latitudes the process of evaporation has 

 anything to do with the vertical movements of these little creatures ? 



For some days I see it noted that about here the sea was very phos- 

 phorescent. It is thought by some that when such is the case, you 

 are unsuccessful with the bag, but I have never found that it makes 

 any difference. 



* Maury. 



