BY E. M. JOHNSTON, F.L.S. Ill 



Sub-Genus. Ctolas. Klein. 

 Valves divaricately striate. 



Genus Lobipbs. Poli. (656.) 

 Shell almost equilateral, cancellated or sculptured by flexuous 

 strice ; iunule short, cartilage quite internal ; teeth 

 one cardinal in the right and two in the left valve ; 

 laterals remote, and sometimes indistinct. Dist. — 

 Atlantic, Mediterranean, W. Indies, Australasia. 



(lxxxvi.) Family TJngtjlinid^;. 

 Genus Mysia. (657.) 

 Shell sub-orbicular smooth ; ligament double, rather long, sub- 

 marginal ; hinge-teeth 2*2, of which the anterior in the 

 left valve, and posterior in the right are bifid ; 

 muscular impressions polished, anterior elongated. 

 Dist. — West Indies, Rio, Britain, Mediterranean, Bed 

 Sea, West Africa, India, Corea, Australia, California. 



(lxxxvii.) Family Eeycinlme. 

 Shell very small, thin, fragile, usually transparent, and some- 

 times gaping, rounded or transverse, laterally 

 depressed; hinge narrow, with one or two cardinal 

 teeth, the lateral more or less elongated, compressed 

 sometimes wanting ; muscular impressions small, not 

 well-marked ; pallial line simple. 



Genus Las^ia. (658-659.) 

 Shell minute and roundish, oval ; beak straight ; cartilage 

 long, placed at the shorter end of the shell, contrary to 

 that in Kellia ; left valve with a minute thorn-like 

 cardinal tooth ; and in each valve two remarkably 

 strong lateral teeth. Dist. — Universal. 



Genus Kellia. (660-661.) 

 Shell small, thin, sub-orbicular, closed, beaks small ; margins 

 smooth ; ligament internal, interrupting the margin, 

 or on the thickened margins ; cardinal teeth 1 or 2, 

 laterals 1 — 1 in each valve. Dist. — Norway, New 

 Zealand, California. 



(Ixxxviii.) Family Ceassatellid*. 

 Genus Ceassatella. (662-664.) 

 Shell solid, ventricose, attenuated behind, smooth or concen- 

 trically furrowed ; Iunule distinct; ligament internal ; 



