1368 CHELIDONOPSIS 



Chet^idonopsis ARiKTiNA ( Rochebniiie) . 



"Shell ellipsoidal, anteriorly siibcompressed, narrow; gaping 

 widely and long ; anterior dorsal angle acute ; posterior region 

 roundly ovoid, enormously gaping; surface concentrically sul- 

 cate with broad sulci : minutely radiately striate ; lateral car- 

 inas twisted backwards in an acute, twisted, sublamellose wing 

 and minutely recticulated on both sides ; dorsal margin straight 

 in front, somewhat concave behind ; epidermis pale shining 

 olivaceous, brownish posteriorly ; nacre iridescent with blue 

 and rose. 



Length 124, height in front 8, in the centre 30, posteriorly 

 33, diam. in front 9, in the middle 17, behind 40, width of pos- 

 terior gape TJ. height 20 mm." (Rochebrune). 



Type locality, Gancini, Congo. 

 Chclidonura arictina Rochebrune, Bull. Soc. Mai. Fr., Ill, 



1886, p. 4, pi. I, figs. 1-4. 

 Chelidonopsis arietina Simpson, Syn., 1900, p. 906. — Germain, 



Bull. Mus. Hist. Nat.. 1908, p. 162, fig. 32 ; Arch. Zool. Exp. 



et Gen., (5), I, 1909, p. 4, pi. i, figs. 1-6. 



"The CJieJidonnra arictina differs from its relative the Cliel- 

 idonura Jiirundo: By its larger size; a shape decidedly ellip- 

 soidal and not simply elongate ; by the acute and not obtuse 

 antero-dorsal angle ; by the size of the posterior wings, the 

 separation, elongation and twisting of the free extremities of 

 the carinas ; by the reticulation of the shell in the parts near 

 the carinas ; by the valves concentrically sulcate and not slight- 

 ly striate ; and finally by its dift'erent color." 



Chelidonopsis hirundo (von Martens). 



Shell elongated, subcompressed, thin, somewhat obovate, 

 slightly inequilateral ; beaks low" or slightly elevated ; posterior 

 ridge pinched up sharply, and narrowly rounded, curving out- 

 wards or ending in a tubular process at its hinder termination ; 

 dorsal line straight, sometimes curved upward in front ; an- 

 terior end very much narrowed, drawn out into a beak above, 

 rounded, gaping and cut away below; base slightly curved; 

 posterior end irregularly rounded, having a wide diamond- 



