11 1G9 



The genus was established by Rang , and the plates XX — XXII have the name of 

 Aclesia; in the text (p. 68) be has retracted the name, referring the species named in the 

 plates to the genus Notarchus of Cuvier, where, however, they do not belong. The genus 

 has mostly been adopted by the malacologists and conchyliologists 1 ) for forms like those 

 originally given by Rang; but no more exact examination has hitherto been made. 



The exterior of the Aclesia is characteristic by the simple or compound tufts or 

 appendages scattered over the back, the rhinophores, and the tentacles; the gill-slit is 

 quite short. Mantle-shield and shell are wanting, and accordingly the gill, the kidney, 

 and the pericardium lie exposed (not covered by the mantle and the shell) in the gill 

 cavity. The foot-sole is not narrow, the foot-lobes which surround the gill-cavity, are 

 quite small. 



The place of the visceral ganglia, as in the Aplysiella, but contrary to the case 

 in the Aplysia, is far forward, between the pleural ganglia. The glans penis is armed 

 with soft cones. 



The Aclesia seem to belong to the warmer seas, and especially to those of 

 the tropics. 



Aclesia ocelligera, Bgh. n. sp. 

 PI. I, Figs. 31—38. PI. II, Figs. 1-11. 



Of this beautifully coloured form a single specimen was obtained on the 25th of 

 Dcbr. 1899 at Koh Chang. 



This specimen had in spirit kept a length of 3 cm , a height of l cm , and a breadth 

 of l-'2 cm ; the length of the rhinophores was 3 mm , of the tentacles 3-5 mm , and of the gill- 

 slit î 1 ™ 1 . The foot was almost as long as the whole body, of which length the tail made 

 5 - 5 mm ; the breadth of the foot in its greatest length was 9 mm , the breadth of the foot- 

 brim l - 5 mm . — The ground-colour was yellowish white, appearing here and there, espe- 

 cially on the fore part of the body, as small spots and narrow stripes, but mostly it is 

 superseded by close-standing black points, which very often form small rings; between 

 the rhinophores, as also on the gill-covers (foot-lobes) groups of somewhat larger black 

 spots with a light halo are seen; such rings are also seen at the base of the tentacles. 

 In the middle between rhinophore and tentacle a fine eye-spot is seen on each side, and 

 along the side of the body a series (6 — 7 in all) of irregularly arranged eye-like spots, 

 moreover 3 — 4 spots of the same kind on the gill-covers. These eye-like spots were round 



') The genus Thallepus of Swainson (A treatise of Malacology. 1S40. pp.250, 359) is often mentioned 

 as being synonymous with Aclesia The characters given by Swainson, are partly incorrect, and 

 quite insufficient; the characteristic tufts on thé back of the Aclesia are not at all mentioned. 



D. K. D. Vidensk. Selsk. Skr., 6. Række, aaturvidensk, og mathem. Afd. XII. 2. 22 



