The OpistJiohranchiata of South Africa. 19 



■breadth of 5 ; one margin is thick, compact, otherwise it is flat, 

 leaflike. 



The colour of this specimen was different from those I also have 

 seen '•- ; the form of the shell, too, somewhat particular, and the 

 stomach-plates difi"erent. Still, it is very likely but a variety of 

 the somewhat variable Dol. Biunphii (Cuv., Rang). 



NOTAKCHID^. 



R. Bergh, Die Opisthobranchiata der Siboga Expedition, 1905, 

 pp. 20-27. 



This group contains the genera Notarchus (Cuv.), Aclesia (Rang), 

 Aplysiella (P. Fischer), and Phyllaplysia (P. Fischer). 



Aclesia, Rang. 



Rang, Hist. Nat. des Aplysiens, 1828, p. 68, pi. xx.-xxii. 



R. Bergh, Malacolog. Untersuch. V. 1900, pp. 352-361.— The 

 Danish Expedition to Siam, 1902, pp. 168-174. — Die Opistho- 

 branchiata der Siboga Expedition, 1905, pp. 20-23. 



Notaeum sicut rhinophoria et tentacula papillis majoribus simpli- 

 ■cibus et compositis instructum ; fissura branchialis brevis. Scutum 

 palliale sicut testa desunt ; branchia, ren et pericardium in cavitate 

 branchiali libera (scuto non tecta). Podarium non angustum. 



Ganglia visceralia antice, inter pleuralia sita. Penis conulis 

 hamigeris armatus. 



The genus was established by Rang, and the plates xx.-xxii. 

 have the name of Aclesia ; in the text he has (p. 68) retracted the 

 name, referring the species named in the plates to the genus 

 Notarchus of Cuvier, to which, however, they do not belong. 

 The genus has mostly been adopted by malacologists and con- 

 ■chologistsf for forms like those originally given by Rang, but a 

 real knowledge of the genus dates from the later years (1900, 

 1902, 1905). 



The Aclesiae belong to the warmer seas, and especially to 



* R. Bergh, "Die Opisthobranchiata der SibogaExpedition," 1905, pp. 13-20, 

 taf. vii., figs. 22-40; taf. viii., figs. 1-9 ; taf. Ix., figs. 1-3. 



t The genus Thallepus of Swainson (" A Treatise of Malacology," 1810, pp. 250,359) 

 is often mentioned as being sj'nonymous with Aclesia. The characters given by 

 Swainson are partly incorrect and quite insufficient ; the characteristic tufts on 

 .the back of the Aclesise are not at all mentioned. 



