120 MOLLUSCA FROM THE CRAG. 



2. Kellia orbicularis, S. Wood. Tab. XII, fig, 9, a — c. 

 Kellia? orbicularis. 5. Wood. Catalogue, 1840. 



_ _ J. Sowerby. Min. Conch., t. 637, fig. 2, a. 1844. 



Spec. Char. Testa minutd, orbiculari, tumidd, obliqud, submquilaterali, clausd ; 

 concentrice et rugose striata; latere postico breviore ; dente cardinali unico in utraque 

 valva ante foveam ligamenti ; fovea triangulari, obliqud, profunda. 



Shell small, orbicular, or spheroidal, inflated, subequilateral, closed ; roughly 

 striated concentrically ; posterior side the shorter ; one cardinal tooth in each valve 

 before the ligament ; ligamental pit oblique, deep, and of a triangular form. 



Diameter, \ of an inch. 



Locality. Cor. Crag, Sutton. 



This is more abundant than the preceding species, and is limited, as far as I 

 know, to one locality. I have not been able to trace it higher up in the Series, 

 or nearer to our own time than the Cor. Crag. A shell called Scacchia inversa, 

 {P/iilippi, En. Moll. Sic, vol. ii, p. 27, T. 14, f. 10,) resembles this in some respects, 

 but differs in others, sufficiently, it is presumed, to be considered specifically distinct, 

 depending upon the figure and description by Philippi. 



The ligament is wholly internal, and the pit for its reception is an oblique, 

 angular depression beneath or within the dorsal margin, extending backwards to 

 some distance, with a ridge or ledge for its support. The umbo is prominent, and 

 there is a considerable obliquity in the shell ; an obtuse kind of ridge slopes from the 

 umbo towards the anterior ventral margin, behind this the shell is a little flattened, 

 giving a squarish outline by a somewhat straightened ventral margin. The left valve 

 has the larger tooth, this is situated a little in advance, and not immediately beneath 

 the umbo ; the cardinal tooth of the right valve is placed further backward, and 

 locks in behind the larger tooth of the opposite valve, making that tooth appear in 

 some specimens to have a ledge, or another rudimentary one. In the figure of this 

 species in Min. Conch., the teeth are represented as of equal size, but there is an evident 

 inequality, neither are they both in the same position, there is no vestige of a tooth 

 on the posterior margin, in which character it differs from any of the three figures 

 given by Brown in his ' Illustrations of British Conchology.' Conrad, in his 

 ' American Miocene Fossils,' figures and describes a similar species under the name of 

 Amphidesma cequata, p. 65, PI. 36, f. 5, but the figure is so inferior, and the descrip- 

 tion so brief, that it is impossible to institute a fair comparison. 



3. Kellia ambigua, Nyst. Tab. XII, fig. 11, a, b. 



Corbula ambigua. Nyst. and West . Nouv. Rech. Coq. Foss. d'Anv., p. 6, pi. 3, fig. 4, 1839. 

 Erycina ambigua. Nyst. Coq. Foss. de Belg., p. 89, pi. 4, fig. f>, a, b, 1844. 



— striatula. Id. - - - - p. 90, pi. 4, fig. 7, b, c. 

 Kellia dubia. S. Wood. Catalogue, 1840. 



— - — /. Sow. Min. Conch., t. 637, fig. 4, a, b, 1846. 



— — Tennant. Strat. List. Brit. Foss., p. 15, 1847. 



