162 OXYNOE. 



liver, which is, however, composed of closely packed ramifying tubes. 

 The group is therefore intermediate between Tectibranchiata and 

 Ascoglossa, but nearer the latter. 



Synopsis of Genera. 



A. Pleuropodial lobes short, not produced in lateral processes ; shell 

 globose-ovate, with a deep sutural sinus above (as in Akera} ; 

 the apex concealed, vertex not umbilicated. Genus OXYNOE. 

 AA. Pleuropodial lobes produced in spatulate or expanded lateral 

 processes ; shell semi-ovate, the lip produced above the vertex 

 but not incised, apex concealed, not terminal. 



Genus LOBIGER. 

 a. Tentacles two. 



b. Lateral pleuropodial processes four, 



Subgenus Lobiger. 

 bb. Lateral pleuropodial processes two, 



Subgenus Dipteropliysis. 

 aa. Tentacles four; lateral processes four, 



Subgenus Pterygopliysis. 



Genus OXYNOE Rafinesque, 1819. 



Oxynoe RAF., Atialyse de la Nature, ou Tableau de 1'Univers et 

 des Corps Organises, 1815, p. 143 (nude name); Journal de Phy- 

 sique, de Chimie, d'Hist. Nat, etc., Ixxxix, 1819, p. 152. Lopho- 

 cercus KROHN, A.nn. Sci. Nat. (3), vii, 1847, p. 55. Icarus FORBES, 

 Rep. Brit. Asso. Adv. Sci., 1843, p. 187 (1844). 



All of the generic names cited above were based upon the Medi- 

 terranean species 0. olivacea. 



Of the six species described, but one is at all fully known ; the 

 shells only of the others being figured. 



Geographic distribution of Species. 



Mediterranean : 0. olivacea. 

 West Indies : 0. antillarum. 

 Indo-Pacific : 0. krohni, 0. viridis, Sandwich Is. 



0. delicatula, Ceylon. 



0. hargravesi, New Hebrides. 



O. OLIVACEA Rafinesque. Frontispiece, fig. 17 ; PI. 11, figs. 43,44, 

 46-50, 58-62 (enlarged). 



