The Cretaceous Fauna of Pondoland. 289 



shallow grooves. Numerous growth-lines cross the ribs and grooves. 

 On the posterior area the ornamentation is less distinct, and on its 

 dorsal part the ribs are narrower and the interspaces wider. Internal 

 margins of valves smooth. 



Length 60-5 . 57 . 44 . 43 mm. 



Height 58 . 51 . 41 . 39 „ 



Affinities. — This species, as mentioned by Griesbach, is allied to 

 Trigonoarca trichinopolitensis (Forbes).^'' It differs, however, in 

 having the umbones distinctly behind the middle of the hinge-area, 

 in the posterior part of the shell being relatively shorter, and in the 

 less rounded character of the anterior margin (especially its dorsal 

 part.) The ornamentation appears to be less developed than in 

 T. tridiinopolitensis , but that may possibly be due to difference of 

 preservation. 



Trigonoarca umzambaniensis (Baily) I may be identical with 

 T. capensis, but unfortunately the type is missing, and Baily's figure 

 is not sufficient to permit a definite opinion. 



Beviarks. — Twelve specimens, including the type which is in the 

 Hamburg Museum, have been seen. 



Genus NEMODON, Conrad. | 



Nemodon natalensis (Baily). 



Plate XXXIV., figs. 3-7. 



1855. Area natalensis, Baily, Q.J.G.S., xi., p. 461, pi. xiii., fig. 2. 

 1904. Latiarca (?) natalensis, Etheridge, Second Eep. Geol. Surv. 

 Natal and Zululand, p. 77, pi. i., figs. 10-12. 

 Description. — Shell stout, sub-quadrate, inflated, inequilateral. 

 Anterior margin curving and passing gradually into the slightly 

 curved ventral margin, and forming with the hinge-line an angle 

 which is rather larger than a right angle. Posterior margin oblique, 

 nearly straight or slightly convex or sinuous, and forming with the 



* Trans. Geo!. Soc, ser. 2, vol. vii. (1846), p. 150, pi. xv., fig. 16. Stoliczka, 

 Cret. Fauna S. India, vol. iii. (1871), p. 353, pi. xviil., ligs. 12, 14, pi. xix., 

 figs. 2, 3, pi. XX., pi. 2, 8, 9, 10. 



t Q.J.G.S., xi. (1855), p. 460, pi. xiii., fig. 1. Etheridge, Second Rep. Geol. 

 Survey Natal and Zululand (1904), p. 76, pi. i, figs. 1-5. 



I Amer. Journ. Conch, vol. v. (1869), p. 97 ; Kerr's Eep. Geol. Survey, N. Caro- 

 lina, vol. i. (1875), Appendix A, p. 3. Meek, Invert. Cret. and Tert. U. Missouri 

 (1876), p. 81. 



