KR. BONNEVIE 



[REP. OF THE -MICHAEL SARS" NORTH 



three specimens were of equal size, about 7 mm. across 

 the shell. 



Localit\ 



Depth 



Date 1910 



• 



Nr. of 



St. 



Lat. N. 



Long. W. 



individuals 



64 

 69 



34° 44' 

 41 s 39' 



47° 52' 

 51° 4' 



150 m. 

 150 m. 



2 % 



2S k 



2 



1 



Atlanta, Lesueur. 



Shell flat, calcified, not nautiloid, but with whorls 

 forming: a more or less protruding" spire on the right 

 side. -- Operculum oval or pear-shaped, with a spiral 

 centre af growth- lines. 



Radula: median plate with only one tooth, 

 intermediate plates with one spine at the free end, 

 and with (or without?) an accessory spine protruding 

 from the concave underside. Lateral plates sickle- 

 shaped, of varying length. 



Of this genus 3 (or 4?) species are represented in 

 the material from the "Michael Sars" Expedition. 



A. peronii, Rang. 

 (PI. I, Figs. 4—7). 



Shell, (fig. 4) flat, 3 — 5 whorls. Spire not protru- 

 ding. The carina does not reach the mouth of the shell, 

 but continues on the other side, gradually tapering, 

 in between the two last whorls, which in consequence 

 are not tightly connected. 



Operculum (fig. 6 a-b) pear-shaped with a spiral 

 centre at its narrower dorsal end. 



Radula (fig. 7). The spine of the median plate 

 is scarcely longer than the lateral horns of the plate 

 itself, the whole thus representing a plate with apparently 

 three spines. -- Intermediate plate with an accessory 

 spine. Length of the lateral plates about 2 /-3 of that 

 of the intermediate ones. 



A. peronii was the heteropod most frequently met 

 with during the "Michael Sars" Expedition, the collection 

 including about one hundred specimens from no less 

 than 18 different stations. Among these were specimens 

 reaching the size of 6—8 mm., but a great number were 

 small, 1 — 3 mm.; and many were represented only by 

 fragments. 



Among the larger specimens several were found with 

 a brown or yellow stripe along the base of the carina, 

 a character wich has been considered as distinguishing 

 the two species A. gaudichaudi, Souleyet, and A. rosea, 

 Souleyet; but the appearance of this stripe is so variable 

 and so many transitions may be found, from the clear 

 white carina of specimens which no doubt belong to 

 A. peronii to others with a carina having a yellow or 



brown base, that I find no reason for considering this 

 stripe alone as a character sufficient to justify the main- 

 taining of these different species. 1 ) 



According to Tesch (1906), A. rosea may, however, 

 be distinguished also by its more protruding spire, and, 

 especially, by a system of fine spiral lines on its inner 

 whorls. But as to A. gaudichaudi the only character 

 distinguishing it from A. peronii, besides the brown 

 stripes, is the absence of an accessory spine on the 

 intermediate plates of the radula. 



I must confess, however, that I do not feel quite 

 convinced of the correctness of the description given by 

 Tesch on this point. The structure of the radula is known 

 to be one of the most reliable characteristics of the natural 

 relations between gasteropod species, and one would a 

 priori not expect to find essential differences between 

 radula-structures in species belonging to one and the 

 same genus. ■ The absence of an accessory spine in 

 some species, 2 ) while it is present in a number of others, 



Locality 



Dept 

 metres 



Date 

 1910 



Number of 

 individuals 



Size 



St. 



Lat. N. 



Long. W. 



mm. 



23 



35° 32' 



7° 7' 



600 



May 5-6 



1 



3 



39 



26° 3' 



15° 0' 



7 



„ 20-21 



1 



? 



45 



28° 42' 



20° 0' 



50 



„ 28-29 



5 



1-4 



„ 



— 



— 



100 



— 



5 



1-5 



48 



28° 54' 



24° 14' 







„ 31 



1 



2 





— 



— 



50 



— 



1 



3 



49 



29° 6' 



25° 2' 







June 1 



1 



6 



„ 



— 



— 



135 



— 



3 



1—5 



, 



— 



— 



185 



— 



32 



1—8 



50 



30° 8' 



31° 19' 



1000(?) 

 



„ 4 



8 

 1 



1—6 



? 



52 



31° 24' 



34° 47' 







„ 6 



5 



2-8 



53 



34° 59' 



33° 1' 



30 



„ 8 



6 



1—2 



56 



36° 53' 



29° 47' 



50 



„ 10-11 



1 



5 



58 



37° 37' 



29° 25' 



1000(?) 

 50 



„ 12-13 



1 

 2 



7 

 6-8 



62 



36° 52' 



39° 55' 







„ 20-21 



4 



1-5 





— 



— 



150 



— 



2 



1—2 



64 



34° 44' 



47° 52' 



1000(?) 

 150 



„ 24 



2 

 16 



4-5 

 1-7 





— 



■ — 



300 



— 



1 



6 



» 



67 



40° 17' 



50° 39' 



500(?) 

 1000(?) 

 100 



„ 27 



1 

 6 

 6 



1 

 2—5 

 2—7 



69 



41° 39' 



51° 4' 



150 



„ 29 



2 



3-7 



81 



48° 2' 



39° 55' 



50 



July 12 



1 



4 





— 



— 



100 



— 



1 



1 



82 



48° 24' 



36° 53' 



50 



„ 13 



3 



1—3 



84 



48° 4' 



32° 25' 



50 



„ 15 



1 



7 



87 



46° 48' 



27° 46' 



100 



, 17 



1 



7 



1 ) Even Souleyet has (fig. 1, pi. 23) figured A. peronii with 

 a yellow base at the carina. 



2 ) According to Tesch in A, a/finis and A, oligogyra, Tesch, 

 and A. gaudichaudi and A. inclinata, Souleyet. 



