TRIBE BRACHTOrODA. 323 



slope inwards ; internal appendage consisting of a single elevated 

 projecting rib. %...%. Brazil. 1 



T. Anomioides. — Orthis A. Scacchi and Phil. 2, p. 69, t. 1.8,/. 9. 

 — T. Appressa, Forbes, Report Brit. As. 1843, p. 193. — Morrisia 

 Seminulum, Davids. — M. A. Gray, Brack, p. 108,/ 17, 18. — Woodw. 

 / 119. Minute, circular, depressed, smooth, olive-green, translucent; 

 perforation large and round, encroaching equally on both valves, area 

 of the upper valve chiefly occupied by it; deltidia rudimentary; 

 lower valve deeply notched at the umbo ; loop consisting of two simple 

 plates attached to the sides of the umbonal notch and to a central 

 bifurcated process. £. Mediterranean.' 2 - 



T. Lunifera. Phil. Sic. I, p. 97, t. 6,/. 16 ; 2, p. 69 (as Orthis L.). 

 — Morrisia L. Gray, Brach.p. 108. Minute, subcordate, compressed, 

 retuse ventrally, bluntly peaked dorsally ; area moderate ; internal 

 skeleton consisting of a • semilunar plate in the centre of the smaller 

 (lower) valve. ^. Mediterranean. 



T. Davidsoni. — Morrisia D. Deslong champs, Ann. N. H. 1855, 

 t. 10, / 20. Transverse, irregularly oval (but variable in shape), 

 coarsely punctate, thin, light yellowish, covered with spinous asperities 

 that are chiefly manifest near the margin. Upper valve convex ; 

 hinge-line straight ; area narrow ; deltidia very small, edging only the 

 very small portion of the foramen existing in this valve. Lower valve 

 flat; with a large circular perforation. |-...tt' Tunis? 



T. Pulchella. Sow. Thes. Conch. 1, p. 360, t. 71, / 105, 6, 7.— 

 Megerlia P. Gray, Brach. p. 104. Subovate, acuminated and 

 rounded dorsally, smooth, whitish, with a few radiating red lines, 

 inequivalve ; margins entire, somewhat flexuous. Upper valve rather 

 flattened, acuminated dorsally, rounded ventrally ; perforation large, 

 incomplete; cardinal area indistinct, its sides rounded; deltidia 

 small, separate. Lower valve somewhat circular ; internal appendage 

 consisting of a single prominent gnomon near the ventral portion. 

 £. Philippines ; Isle of Cocos. " Loop small, trebly attached " (Gray). 



1 The genus Bouchardia of Davidson was formed for this species. 

 " Beak prominent, with a minute apical foramen ; deltidium blended 

 with the shell ; apophysis anchor- shaped, the central septum being 

 furnished with two short lamellae. 



2 This and the two following are the only known recent species of 

 Davidson's subgenus Morrisia. " Shell with a large foramen en- 

 croaching (equally for the most part) on both valves ; ventral (upper) 

 valve with a small straight area ; loop not reflected, united to a small 

 forked process in the centre of the valve ; structure coarsely punc- 

 tate " (Gray). 



