188 PERCY SLADEN TRUST EXPEDITION 



Atlanta helicinoides, Stat. u. 



Atlanta turriculata, Stat. P. 



Atlanta inclinata, Stat. u. 



Atlanta gibbosa, Stat. u. 



Cardiapoda trachydermon, Stat, hh, 



Cardiapoda sublcevis, Stat, y, 



Firoloida koivalewskyi, Stat. A, Q, a, x, dd, ee. 



Of the stations here named, only A, a and dd were worked during the daytime*. 

 Firoloida koivalewskyi was the only species taken during these hours, whilst all other 

 species were obtained exclusively at night or by heaving in the pelagic nets from a depth 

 of 50 — 1000 fins. Oberwimmer's experience in the Mediterranean seems therefore to refer 

 to a fairly general rule, according to which the Heteropods effect daily vertical migrations 

 like the Pteropods and other pelagic organisms. It is clear, however, that we must wait 

 for much more information before forming our conclusion. Only it may be supposed 

 perhaps that the richer catches of Heteropods in the Amirante Group are due to a 

 frequently employed method of pelagic fishing during many hours of the night ; at least 

 we cannot think that the waters around these islands should be richer in Heteropods than 

 other parts of the ocean. 



As to the normal depth to which the Heteropods descend we know as yet very little. 

 The Sealark caught species of Atlanta and Firoloida if the pelagic net was sunk down to 

 a depth of 1000 — 900 fins, and heaved in to the surface, but of course it is impossible to 

 say at which depth the specimens got in the net, as no closing nets were used. Further 

 we have some notes about the bathymetrical occurrence of Carinaria mediterranea off 

 the coast of Irelandf, where this species is recorded to live at depths of 768, 550, 450, 345 

 and 100 fms. The temperature in such depths of more than 700 fins, we may assume to 

 be rather unsuitable for such typical warm-water organisms. 



EXPLANATION OF PLATES 12—14. 



Plate 12. 



Fig. 1. Desmopterus gardineri, n. sp., from the hind side, x 16. 



Fig. 2. Head and part of fins of same, proximal view, x 25. Explanation of letters in figs. 1 and 2. 



accgl. accessory sexual gland ; b.m. buccal mass ; yon, gonad ; h.gl. hinder gland ; int. intestine ; 



m.o. mouth opening; nephr. kidney; o.int. opening intestine; p. penis; st. stomach; t. tentacle. 

 Fig. 3. Oxygyrus rangi, from the left side; animal withdrawn within its shell, x 40. 

 Fig. 4. Cerebral ganglia and eyes of Cardiapoda sublcevis. x 18. cbg. nerve to the buccal mass ; 



eg. cerebral ganglion ; le. lens ; mt. muscles to the tentacle ; ne. optic nerve ; not. nerve to the 



otocyst ; nt. nerve to the tentacle ; ot. otocyst ; t. tentacle. 

 Fig. 5. Visceral nucleus of same, from the right, x 35. a. anus ; g. gills ; int. intestine ; k. kidney ; 



ok. opening kidney to the exterior; vg. visceral ganglion; vn. visceral nucleus. 



* Unfortunately the hour of Stat, n has not been recorded. Yet it would be most interesting to know 

 it, as here a great many specimens, apparently a swarm, of Atlanta were obtained. [6 — 8 a.m. j. s. B.j 



t Miss Anne L. Massy, The Pteropoda and Heteropoda of the Coasts of Ireland, Fisheries, Ireland, 

 Sc. Invest. 1907, ii. (1909), pp. 50, 51. 



