214 LUCINID^. 



grooved ; the ligament must have been thin, for there is only a 

 short A^ery narrow space immediately beliind the beaks for its 

 attachment, no special nymphoe being present. 



Differs from IJnicardium in the number and position of the 

 hinge-teeth. 



CoRBiCELLA, Morris and Lycett, 1853. 



Etym. — Diminutive of Corbis. 



Bidr.— Fossil, 1 sp. Upper part of Inferior Oolite — 

 Oxfordian ; England, France. C. subsequilatera, Lycett 

 (cxix, 60). 



Shell destitute of ornament, ovately elongated, rather com- 

 pressed ; anterior side small ; hinge characters differ from those 

 of Corbis, in the absence of the anterior lateral tooth, and in the 

 oblique internal ridge passing downwards behind the anterior 

 muscular scar. 



Corbicella is intermediate between Corbis and Tancredia ; 

 and from the latter, to which it is more nearly allied, it is sep- 

 arated by its more ovate form, and by the absence of the 

 posterior oblique angle, and in the possession of a lengthened 

 hinge-lamina and depressed remote posterior lateral tooth. 



Morris and L^^cett state the anterior lateral tooth is always 

 wanting, but though not well developed, it is certainly indicated 

 by the internally strongly thickened margin in such species as 

 Gorh. dejjressa, Desh., and still more in Gorb. Barrensis, Buv. 



Sportella, Deshayes, 1852. 



Distr. — Fossil, IT sp. Tertiary; Paris Basin, S. Gailleti, 

 Desh. (cxix, 61). 



Shell oblong, smooth, depressed, subequilateral ; valves closed. 

 Hinge narrow, with two unequal, diverging teeth in the left 

 valve, one in the other ; the lateral teeth are wanting. Muscular 

 scars large, oval, nearly equal ; pallial line simple. Ligament 

 external. 



Possibly some of the Liassic species referred to Unicardium 

 belong to this genus. 



Sph^rella, Conrad, 1838. 



Distr. — 3 recent sp. California, Gruayaquil, IS". Zealand. 

 Cretaceous, Tertiary; United States, Europe. G. concentrica, 

 Conr. (cxix, 63). 



Shell rounded, tumid, thin ; hinge with two cardinal teeth in 

 each valve, the posterior one in the right valve broad, bifid, par- 

 allel to the hinge-margin, in the left single, but equall}^ elongated. 

 Some of the palaeozoic Lucinse may belong to this genus. Conrad 

 and others class it near Diplodonta, but the prolonged posterior 

 teeth appear to indicate a greater relation for the various Corbinse. 



