26 



KR. BONNEVIE. 



[REP. OF THE "MICHAEL SARS" NORTH 



Station 



23 



29 



45 



47 



49 



52 



53 



56 



58 



64 



67 



81 



Date 



%-* 



75— 10 /o 



2S/ 5 _S9/ 5 



30 /5 



Ve 



"As— % 



Ve—Ve 



w k— ll /e 



"/.— 13 /g 



2 Ve 



27 /6 



"h 



N 

 Position w ' 



35° 32' 



7° 7' 



35° W 

 7° 55' 



28° 42' 

 20° 0' 



29° 2' 



22° 53' 



29° 8' 

 25° 16' 



31° 24' 



34° 47' 



34° 59' 

 33° 1' 



36° 53' 

 29° 47' 



37° 37' 



29° 25' 



34° 44' 

 47° 52' 



40° 17' 



50° 39' 



48° 2' 

 39° 55' 



Depth in m. 



0— 50 



50— 100 













1 



1 

 6 













— 







■ 



— 



— 



1 



1 



2 











1 



100— 250 

 250— 500 

 500— 750 



22 



1 



1 



— 



24 



— 



— 



— 



— 



1 

 4 



— 



— 



2 









— 



— 



— 















2 



— 



750—1000 



— 





— 



— 



— 



— 



— 



— 



— 



— 



— 



— 



1000-1250 



— 



— 



1 



— 



1 



— 



1 



— 



— 



8 



— 



— 



1250—1500 



— 



— 



— 



1 



— 



— 



— 



— 



— 



— 



— 



- 



Number of individuals of Cuvierina columnella. 



Cuvierina Boas. 



Cuvierina columnella Rang. 



As in the genus Clio (subgenus Euclio), we find in 

 Cuvierina columnella 1 ) a small membranous lobe(gill) inside 

 the mantle-margin on the right side of the body; this lobe 

 has been observed by Pelseneer (1888) and by Tesch (1904). 



Cuvierina culumnella was found during the "Michael 

 Sars" expedition generally distributed along the African 

 coast and the southern crossing of the ocean from the 

 Canaries to Newfoundland, thus agreeing with what was 

 previously known about its distribution (Meisenheimer 

 1905), but its occurrence at Station 81 (lat. 48° 2' N.) is 

 farther north than any former record. 



Cavolinia Abildgaard. 



Subgen. 1 : Diacria Gray. 



Cavolinia (Diacria) trispinosa Lesueur. 

 PI. II, fig. 13-14, pi. IV, fig. 28-34. 



Certain features in the anatomy of this species remind 

 one of Clio falcata, the foot being developed into a 

 broad and continuous swimming-plate, the dorsal part of 

 which is tightly folded during rest and covered by the 

 large and rigid ventral lobe, while the pallial gland 

 with its vividly coloured transverse striation resembles that 

 of Clio falcata. The resemblance is even greater when 

 young individuals of Diacria trispinosa (pi. II fig. 13—14) 

 are compared with full-grown specimens of Clio falcata 

 (fig. 11 — 12), for the shape of the body, the development 

 and striation of the pallial gland, and above all its 

 extension on the right side of the body, indicate a 

 close relationship between them. Also in Diacria trispi- 

 nosa a lobe-like gill protrudes from under the mantle- 

 margin on the right side of the body. 



During the "Michael Sars" expedition several hundreds 

 of individuals of this species were preserved, a consider- 

 able proportion having diminutive soft bodies within fully 

 developed shells (fig. 29, pi. IV). 



At first I did not pay much attention to these aber- 

 rant forms, considering them as degenerate individuals, 

 but I soon observed a series of transitions between them 

 and the normally developed, forms (fig. 29 — 34, pi. IV). 

 A thorough investigation proved the small soft bodies to 

 be in a state of vigorous development and not degenerate, 

 all the organs being present and well preserved, although 

 of small size (fig. 33). 



A consideration of the soft bodies alone leaves no 

 room for doubt that the series shown in pi. IV illustrates 

 the normal development of Diacria trispinosa. The shells 

 also show a gradual development, from the hyaline and 

 quite colourless shell of fig. 29 to the normally pigmented 

 one of fig. 34, and I am indeed inclined to believe that 

 the individuals with small bodies within large shells 

 represent normal stages of development, although I have 

 seen no figure illustrating the transition between the two 

 stages represented in fig. 28 and fig. 29. 



But here the questions arise: How does the shell 

 grow, and what laws govern the development of its 

 characteristic shape and size, so far ahead of the body? 

 Does additional fluid secreted by the animal suffice to 

 produce an independent marginal growth of the shell, 

 following laws as fixed as those governing the growth 

 of a crystal? The answers to these questions must be 

 left for future investigation. 



Geographical distribution. Like Clio pyra- 

 midata this species seems to be generally distributed, 

 but in lesser numbers, all over the North Atlantic. 



During the "Michael Sars" expedition it was taken 

 at no less than 24 stations, covering the whole route 

 along the European and African coasts and the southern 



l ) Special traits of the anatomy of Cuvierina columnella will be considered in a later paper. 



