230 ACT^ONID^E, AKERATID^. 



ADELACT^ON Cossmann, 1895. 



Ess. Pal. Comp., p. 54, type A. papyraceus Bast., Miocene. 



Proposed as a substitute for Myonia A. Ad. non Dana, see Vol. 

 xv, p. 1 67. Includes several Miocene species, the recent A. concinna 

 Ad. (Vol. xv, p. 172) of Australia, and several Japanese forms (see 

 Vol. xv, p. 169, 170). 



Genus KLEINELLA A. Adams (Vol. xv, p. 179). 



Cossmann, in his excellent Essais de Paleoconchologie Comparee, 

 pt. 1, p. 44 (1895), has been able, by the assistance of Messrs. R. 

 B. Newton and E. A. Smith, to figure the type of this genus, K. can- 

 cellaris Ad., and to determine the fact that it does not belong to the 

 Actceonidce, but is allied to Menestho. His figure of K. cancellaris is 

 reproduced in figure 6 of Frontispiece. For description see Vol. xv, 

 p. 180. 



Actceon aplisiformis Fer., Tab. Syst., p. xxx=Elysia viridis Bosc. 



Aetceon viridis Fer. 1. c. (Laplysia viridis Mont.) Y?/sia, a nudi- 

 branch. 



Family AKERA TIDJE Pilsbry, (Vol. xv, p. 350). 

 Genus AKERA (Vol. xv, p. 376). 



A. BULLATA Mu'ller (Vol. xv, p. 377). 



Var. nana Jeffreys. Length ^ inch. 



Var. farrani Norman. Length If inch. (==A. bullata var. 

 gigantea Norman, Mus. Normanianum, iv, Moll. 1888, No. 101). 



The variation in size in this species is most extraordinary, and 

 perhaps the forms here treated as varieties should rather be regarded 

 as entitled to rank as species. The full size of ordinary specimens 

 may be taken as an inch ; but no specimens of var. nana which were 

 dredged by Jeffreys and myself in shallow water at Balta Sound, 

 Shetland, exceed three-twentieths of an inch. On the other hand, 

 Dr. Farran found many years ago (see Nat. Hist. Review, Vol. iv, 

 [1857] p. 74) the gigantic variety which I here name after him. 

 The specimens were dredged near Birterbuy Bay, Ireland; the 

 animal measured 3 inches long and 2 wide, and weighed 2J ounces. 

 The shell of one of these giants now in my collection measures If 

 inches long and an inch wide ; hundreds of specimens of var. nana 



