ATLANT. DEEP-SEA EXPED. 1910 VOL. 



HETEROPODA 



would be rather surprising, and the drawings by Tesch 

 (1906, pi. VII, fig. 10 and 13, pi. VIII, fig. 16 and 26) 

 are unfortunately not clear enough to serve as unquestion- 

 able proofs on this point, the lateral plates of the radula 

 in his drawings concealing the part of the median plate 

 where an accessory spine might be found. Until this 

 negative character of A. gaudichaudi is definitely proved, 

 its rank as a species different from A. peronii must 

 therefore be questioned. 



A. peronii was during the "Michael Sars" Expedition 

 found scattered within the upper layers (10 — 300 m. in 

 depth) of the Atlantic, as far north as lat. 48° 24' N. 

 At some stations (st. 49, 56, 62, 64), where it seems to 

 have been brought up from greater depths (1000 m.), 

 the specimens in question may have been caught during 

 the passage of the gear towards the surface. 



Atlanta fusca, Souleyet. 

 (PI. I, figs. 8—9). 



This well-defined species is represented by one small 

 specimen, the body of which was in a very frail condition. 

 My attempts at preparing the radula of this specimen 

 were therefore not successful. 



The shell of A. fusca is translucent, of a yellowish 

 colour. The number of whorls is 3 — 4, the spire somewhat 

 protruding beyond the width of the body-whorl. Carina 

 gradually tapering towards the shell-mouth and encircling 

 the entire body-whorl. On the inner part of the latter, 

 as on the spire-whorls, there is a system of fine longi- 

 tudinal stripes visible on both sides of the shell. The shell- 

 mouth is ovoid, instead of pear-shaped as in other species. 



The operculum is, in conformity with the ovoid 

 shell-mouth, broadly oval, with the spiral lines centred 

 at a considerable distance (about 1 — 3) from the upper end. 



Radula unknown. 



Locality 



Depth 

 metres 



Date 1910 



Nr. of ind 



Sixe mm. 



St. 



Lat. N. 



Long W. 





52 



31° 24' 



34° 47' 







% 



1 



2 



Atlanta macrocar/nata, n. sp. 



(PL I, figs. 10—13). 



Shell white, transparent, very fragile, with 5 — 6 whorls 

 forming a broadly cone-shaped spire. The body-whorl is 

 only loosely connected with the spire, the largest specimens 

 having a deep slit not filled by the carina, which separates 

 the mouth part of the shell from the spire. Carina broad, 

 encircling the whole body-whorl, on one side continuing 



to the shell-mouth, on the other side gradually, though 

 rather steeply, tapering towards the beginning of the 

 second whorl (figs. 10 — 11). 



Operculum broadly pear-shaped, exceedingly clear 

 and transparent; the spiral centre lying at a distance (about 

 1 /i of the height) from its upper end (fig. 13). 



The radula (fig. 12) is of the typical Atlanta shape, 

 but relatively much smaller than in other species of Atlanta. 

 Median plate with one spine and short lateral horns. 

 Intermediate plates with accessory spine, and lateral 

 plates the shortest of which is more than half as long 

 as the intermediate plate. 



This species, so well characterized by the broad carina, 

 which does not taper towards the shell-mouth, by the 

 cone-shaped spire, and by the loose connection between 

 the latter and the body-whorl, is represented in the 

 "Michael Sars" collection by about 20 individuals, inclu- 

 ding many fragments, all from one station. 



The largest specimens measured up to 2 mm., most 

 of them did not, however, exceed 1 mm. 



Locality 



Depth 

 metres 



Date 1910 



Number of 



St. 



Lat. N., 



Long. W. 



individuals 



64 



34° 44' 



47° 52' 



150 



2 Vg 



ca. 20 



Atlanta, sp. (?). 



(PL I, figs. 14-15). 



From one station near the Azores there is a fragmen- 

 tary specimen, which by its operculum and radula proves 

 to be different from all the species just mentioned. Its 

 shell was, however, broken, hence a full comparison with 

 other known species is excluded. 



The colour of the shell is white. Its shape unknown. 



The operculum (fig. 14) is pear-shaped with the 

 spiral centre at the upper end more finely striped than is 

 the case in A. peronii. 



The radula (fig. 15) is relatively large, especially its 

 intermediate plates, which are of the typical shape 

 with accessory spines. Median plate with one tooth 

 considerably longer than the corners of the plate. 



Lateral plates relatively short, the shortest about 

 half the length of the intermediate plate. 



Locality 



Depth 

 metres 



Date 1910 





St. 



Lat. N. 



Long. W. 





56 



36° 53' 



29° 47' 



50 



icui/a 



One fragment 



