12 



KR. BONNEVIE. 



[REP. OF THE "MICHAEL SARS" NORTH 



remind one of Peraclis more 

 than of other species of Lima- 

 cina. The same is true also of 

 the position of the pallial 

 cavity on the right side of 

 the bod}-, a point of special 

 interest which will be further 

 discussed later on. 



As will be shown below both 

 these characters are found also 

 in a species of the Cavoliniidae, 

 viz.: Clio falcata, with which 

 L. helicoides seems to have 

 several traits in common. The 

 want of an operculum in 



L. helicoides is also a character pointing towards a rela- 

 tion with the Cavoliniidae. 



Geographical distribution. Shells of L. heli- 

 coides have previously been found along the eastern coast 

 of the Atlantic ocean, from Ireland and the Bay of Biscay 

 (Jeffreys, Pelseneer) to the Congo and Cape (Meisen- 

 heimer), and off the Azores (Pelseneer); its existence off 

 the American coast (Georgia) is questioned (Dall). 



During the "Michael Sars" Expedition complete 

 animals of this species were taken at eight stations all 

 in the western part of the Northern Atlantic. As will be 

 seen from the table it does not belong to the surface 

 plankton, but was taken in depths of 400 to 1500 m. The 

 hydrographical conditions show that L. helicoides belongs 

 to a water-layer with a temperature below 10° C. (textfig.38). 

 Its occurrence in the western part of the ocean only, and 

 at a depth so shallow as 400 m. is seen to be in accordance 

 with the extension of the water-layer mentioned. 



Limacina helicina Phipps. 



A few small specimens of this arctic species were 

 taken near Newfoundland, within or near the cold Labrador 

 current. 



St. 80. 47 s 34' N„ 43° 1 1' W. Depth 300 m. 13 individuals. 

 St. 81. 48" 2' N., 39° 55' W. „ 50 m. 1 



Limacina retroversa Flemming 

 and Limacina balea Moller. 



With regard to the nomenclature of these two forms 

 the opinions of different authors are widely divergent. 

 They are used as the names of two distinct species or as 

 synonyms of one and the same species. At the same 

 time the names of other species, such as L. trochiformis, 

 L. australis, L. mac andrei, are variously used as synonyms 

 of one or the other or of both these names. 



Large quantities of this (or of these two) species are 

 included among the material from the "Michael Sars" 



Station 



62 



64 



66 



67 



80 



81 



82 



84 



Date 



20/ G _21/ 6 



24 /e 



26 /« 



27 /s 



n/ 7 



12/ 7 



13/, 



15/ 7 



Position v,; 



36° 52' 



39° 55' 



34° 44' 



47° 52' 



39° 30' 

 49° 42' 



40° 17' 

 50° 39' 



47° 34' 

 43° 11' 



48° 2' 

 39° 55' 



48° 24' 

 36° 53' 



48° 4' 

 32° 25' 



Depth in m. 

 0— 50 



















50— 100 

 100— 250 



— 



— 



— 



— 



— 



— 



— 



— 



250— 500 



— 



— 



— 



1 



— 



— 



— 



— 



50((— 750 



1 



— 



3 



4 



— 



— 



7 



7 



750—1000 



— 



— 



1 



— 



— 



— 



1 



4 



1000—1250 



2 



1 



— 



— 



1 



1 



— 



1 



1250—1500 



— 



1 



— 



— 



— 



— 



— 



1 



Number of individuals of Limacina helicoides. 



Expedition, and I have taken the opportunity of trying 

 definitely to settle the question about the identity or 

 distinctiveness of the two forms originally described as 

 L. (heterofusus) retroversa Flemming, and L. (Spinalis) 

 balea Meller, and possibly also about their relations to 

 the other forms whose names have been combined with 

 theirs. The results of my investigations prove that L. 

 retroversa, and L. balea must be considered as two different 

 species, very nearly related but yet distinct in shape as 

 well as in occurrence. 



In the original descriptions Heterofusus retroversus 

 was by Flemming (1823) characterised and figured as a 

 "shell with five rounded whorls", which "increase some- 

 what rapidly in size", while Spinalis balea according to 

 M0ller (1841) has a shell "with 7 cylindrical gradually 

 increasing whorls". 



Just the same difference is pointed out also by Gould 

 (1870) in his description of the genus Heterofusus. H. 

 balea is described as having (pag. 505) "whorls seven, 

 sculptured by minute distinct, impressed, revolving lines; 

 last whorl large; aperture about equalling the spire, obtuse 

 in front". H. retroversus is described as having "the 

 body whorl very ventricose; the spire of four whorls, but 

 not forming half the length of the shell". 



Agreeing with the previous authors with regard to 

 the number and shape of the whorls, G. O. Sars (1878) 

 holds that the most constant character distinguishing the 

 two species is to be found in the sculpture of their shells, 

 — the shell of L. balea being finely but very distinctly 

 spirally striated, while in L. retroversa such a striation is 

 only very slightly indicated. 



Boas (1886) on the other hand maintains that there 

 exists no real distinction between the two species, com- 

 plete series of transitions being found between forms with 

 long and short spires as well as between those with and 

 without a distinct striation. 



