304 Annals of the Sonth African Miiseum. 



Family VENEKID^. 



Genus MEEETEIX, Lamarck. 



Mebetkix umzambiensis, sp. nov. 



Plate XXXVI., figs. 4-6. 



Description. — Shell stout, convex, more or less triangular, with 

 rounded margins, very inequilateral. Lunular margin deeply con- 

 cave. Postero-dorsal margin long, curving, forming an obtuse angle 

 with the posterior margin, which is curved and passes gradually 

 into the ventral margin. The latter, together with the anterior 

 margin, make a strong and regular curve. Anterior extremity 

 rounded. Umbones pointed, with a strong anterior curvature. 

 Lunule large, cordate. Escutcheon large, depressed, with a sharp 

 edge. 



Surface smooth, except for growth-lines, some of which, at fairly 

 regular intervals, are more distinct than the others. Sometimes 

 small ribs are present, especially near the margin of the lunule. 

 The lunular tooth in the left valve is long and stout. 



Length 61 . 58 . 51 . 48 mm. 

 Height 54 . 52 . 48 . 43 „ 



Affinities. — This species is similar to M. plana (Sowerby)" from 

 the Blackdown Greensand, but is distinguished (1) by its large, deep, 

 and sharply limited escutcheon, (2) by the greater anterior curvature 

 of the umbones, (3) by its more concave lunular margin, (4) by the 

 greater relative height of the valves, (5) by its stouter shell, and 

 (6) by the longer lunular tooth. 



Specimens of Meretrix [Cytherea] from Southern India have been 

 referred to M. plana by Stoliczka t and his figures appear to agree 

 closely with some examples from Blackdown, but I have had no 

 opportunity of examining any Indian specimens. Holzapfel also 

 identifies specimens from the Aachen Greensand with M. plana. 



In the character of the escutcheon M. umzambiensis resembles 

 M. Benauxiana (d'Orbigny).| 



M. umzambiensis is similar to M. polymorpha (Zittel), j from 



* Min. Conch, vol. i. (1813), pi. xx. (lower figures), p. 58. 

 t Cret. Foss. S. India (1870), p. 169, pi. vii., figs. 1-4. 



J Prodr. de Pal., vol. ii. (1850), p. 194 ; Pal. Fran^. Terr. Cret. vol. iii. (1845), 

 p. 447, pi. ccclxxxvi. figs. 1-3. 



S Bivalv. Gosaugeb., pt. i. (1865), p. 126, pi. iii. fig. 6. 



