BIVALVIA. 143 



2. Cardita alticostata, S. Wood. Tab. XXI, fig. 3. 



Spec. Char. C. Testa minima, orbicularis turgidd, suhincequilaterali, radiatim costatd, 

 costis circa 13 elevatis acutis compressis utrinque nodalosis ; umbonibus minutis, obliquis, 

 depressis, subincurvatis ; lunula minutd. 



Shell small, orbicular, and nearly spherical, nearly equilateral, costated with about 

 13 elevated ribs; beaks small, oblique, depressed, slightly incurved; lunule small. 



Diameter, -jth of an inch. 



Locality. London Clay, Highgate [Edwards). 



One pretty little specimen is in Mr. Edwards's cabinet, and this appears to me to be 

 entitled to a specific position ; its principal distinction is an elevated and compressed rib, 

 the lower part of which is angular ; on the top of this angle is an elevated ridge, not very 

 sharp ; on each side of these ridges are some large and distinct nodules, but the centre is 

 smooth. 



3. Cardita Brongniartii, Mantell. Tab. XXII, fig. 9. 



Cabdita Brongniartii, Mant. Geol. of the South East of Engl., p. 368, 1833. 



— — J. Sow. In Dixon's Geol. of Suss., pp. 116, 225, t. xiv, 



fig. 33, 1850. 



Spec. Char. C. Testa transversa, irregulariter ovatd, vel oblique subtriangulatd, valde 

 inaquilaterali, crassd, tumidiusculd ; siphoni-regione subangulatd ; radiatim costatd, 

 costis 30 — 32 depressis, rugosis ; umbonibus subprominentibus lunula minima prof undd ; 

 car dine crassiusculo. 



Shell transverse, irregularly ovate or obliquely subtriangular ; very inequilateral, thick, 

 slightly tumid, siphonal region roundedly triangular ; costated, ribs about 30, rough and 

 depressed ; umbones not prominent ; lunule heart-shaped, small and deep ; hinge mode- 

 rately thick. 



Length, 2 inches ; height, \\ inch. 



Localities. London Clay, Bognor. Var., fig. 12, a, b, Tab. XXII, Clarendon. 



This species is, I believe, peculiar to England, and it has been long known from the 

 locality of Bognor. Mr. Edwards's cabinet contains also a large suite of specimens from 

 Clarendon. This latter shell is here placed as a variety ; it differs somewhat in form, 

 being less elongated, and has considerable resemblance to planicosta, but it is never so 

 large as that species, nor the ribs so flat. Called by Mr. Edwards Clarendonensis. 



