287 



"This genus difieif from c<i//i*(i,/<i.>- in having the eaves nl. 



the ttvth straight 'th-Hi-h i'iv.|nent ly |.n.|.prd oiit.-id.', a- in f 

 . the mantle en.udrd with minute Imni; 

 and furnished wit 1. lichen round tin- -utiir<-<. 



anterior valves is 5 slit, M in Aruntli"i-i,;t,--, hut that may be only a 

 specific peculiarity. The 7A///A//./ variabiKt Ad. and Am'. I'. /.. 9 

 1- SI ''I. p. 1!M, pn.hably belongs to this genus hut ha- not been 

 dissected. Angasia is known at once from Hanlwja by the presence 



of insertion teeth ; and from /'/,/,-/'/, / io /v/ hythe regular articular i-.n 

 of the tail plate. If the genera be grouped according to the raanth- 

 poivs Ant/'i*I'i will n-pn-sont Chatto/,/*,!,-,/ in the tufted series, as 

 Callistoplax represents (.'<tt/!*trlitton." 



A. TETRICA Carpenter, n. sp. PI. 61, figs 27-32 (sculpture not 



represented.) 



Shell oval, greenish-ashen, rather elevated, the jugum acute ; 

 mucro slightly in front of the middle, slightly elevated ; valves 

 squared, beaked ; the terminal ones much flattened. Jugular area 

 obscurely tricostate ; lateral areas obscurely defined by a diagonal 

 angle ; anterior valve somewhat obsoletely five-angled ; the whole 

 surface very closely sculptured with wide, irregular, flattened some- 

 times striated pebbles, smaller toward the dorsal ridge. 



Interior: Posterior valve having 9-13 slits, the teeth small, 

 radially flattened, rugose outside and propped, generally bilobate ; 

 anterior valve having 5 slits, the teeth more acute, roughened out- 

 side, slightly propped ; central valves with one slit, the teeth acute, 

 rugose outside, conspicuously thickened or propped at the sides of 

 the slit; eaves small; sinus narrow, short, smooth; sutural plates 

 separated. 



Girdle narrow, leathery, with very close and very minute cor- 

 neous scales ; at the sutures and around the end valves there are 

 bunches composed of a few short spicules, and there are a few 

 scattered spicules also. 



Length 15, breadth 9$ mill.; divergence 120 (C 



Ceylon (Mus. Curaing, No. 83). 



A. tetrica CPR. MS:, and in DALL, Proc. U. S. Nat Mus., 1881, 

 p. 286 (no description). 



A common observer might describe the mantle .simply as rough 

 and leathery, so minute are its remarkable features. T 



