ATLANT. DEEP-SEA EXPED. 1910. VOL. Ml 



MURAENOID LARVAE. 



39 



In this table the stations have been arranged in five 

 apparently natural groups, the number of individuals and 

 species taken in each group being indicated at the foot. 



The three southern groups are distinguished at once 

 from the two northern groups by the greater number of 

 individuals, and especially by the large number of species, 

 and this difference is still more clearly brought out by 

 combining the results obtained at the three southern groups 

 as compared with the two northern groups. Thus, 169 

 individuals belonging to 25 species were taken in the 

 southern groups (Stats. 34 to 67), whereas only 32 indivi- 

 duals belonging to 4 species were taken in the northern 

 groups (Stats. 81 to 98), so that nearly all the species 

 represented in the collection, and the large majority of the 

 individuals were taken in the southern groups of stations. 

 It may be added that, according to Danish and Norwegian 

 investigations (Schmidt 31), Leptocephalus Anguillae vul- 

 garis and L. Congrl vulgaris have probably immigrated 

 into the northern groups from the south. 



Judging from the "Michael Sars" material, there can 

 be little doubt that the northern limit of distribution for 

 most of the species occurring in the North Atlantic lies 

 somewhere between the northern and southern crossings. 



Besides the frequently occurring species L. Anguillae 

 vulgaris, L. Congrl vulgaris and L. Synaphobranchl pin- 

 nati, only 13 larvae belonging to five species have, as far 

 as I am aware, been taken to the north of lat. 45° N., viz., 



Leptocephalus Holti, 



— rostratus, 

 latlsslmus, 

 thorianus, 



— enchodon. 



1 specimen, Schmidt (27). 

 2 



1 — 



Autor. 



From localities south of lat. 45° N. in the Atlantic, 

 we have records of a multitude of species besides the 25 

 species described here, viz., 



Leptocephalus immaculatus, Stromman (33) 



— Scheelei, 



— Forsstroml, — 



— undulatus, 



— crenatus, 



— fuliginosus, — 



lanceolatus, — , Schmidt (29) 



— hyoproroides, 

 tiluroldes, 



— Grassi, Eigenmann and Kennedy (9) 

 dipthychus, — 



rex, — 



amphioxus, — 



— caudomaculalus, — — 

 latus, — — 



Leptocephalus Gilli, Eigenmann and Kennedy (9) 



Strommani, — 



Elgenmanni ■ — 



(renamed by Autor) 

 mucronatus, Eigenmann and Kennedy (9) 

 discus, — 



humllis, 



Gilberti, — 



ingolflanus, Schmidt (29) 



— Andreae, 



Chlopsis bicoloris, — — 



hjorti, Blegvad (1) 



In the Atlantic Ocean between 0° and lat. 45° N. 

 we have records of the capture of 52 species altogether. 

 Although the same species may possibly have been given 

 two names, still the above list illustrates the immense 

 difference between the leptocephalid fauna of the northern 

 and southern parts of the North Atlantic, which is plainly 

 shown by the "Michael Sars" material. 



Bathymetrical distribution. 



As already indicated, during the expedition of the 

 "Michael Sars" series of nets fastened at intervals to the 

 wire were dragged simultaneously through the water (for 

 particulars see Murray and Hjort (23). The arrangement 

 at different stations was not always the same, but usually 

 the following plan was adopted: — 



At the surface, a silk-net 1 metre in diameter; 

 with 100 metres of wire out, a — 1 — „ — 



200 -„- a — 1 — „— 



300 — „ — Petersen's young-fish trawl; 



600 — „— a silknet 3 U metre in diameter; 



„ 1000 — „ — young-fish trawl 



„ (1500 — „ — a silk-net 3 /4 metre in diameter); 



,, 2000 — „ — young-fish trawl 



„ 2500 — „— a silk-net 3 /i metre in diameter; 



„ 3000 — „— a shrimp-net 3 metres — „ — 



Any sources of error due to the fact that the nets 

 functioned during the descent and ascent, as well as while 

 being hauled horizontally, have been as far as possible 

 eliminated by prolonging the duration of the hauls, which 

 sometimes lasted twelve hours, but still there is a possibi- 

 lity that some of the larvae have been taken in lesser 

 depths than those assigned to them in the accompanying 

 table. 



The depth at which a net may be towed horizontally 

 will depend on the speed of the vessel, on account of 

 the friction of the net and wire against the water, and 

 on the length of wire between the vessel and the net. 



