ANGASIA. 287 



" This genus differs from Callistoplax in having the eaves short, 

 the teeth straight (though frequently propped outside, as in Callo- 

 vhiton), the mantle crowded with minute horny scales or rudimentary 

 bristles and furnished with pore-bunches round the sutures. The 

 anterior valves is 5 slit, as in Acanthochites, but that may be only a 

 specific peculiarity. The Hanleya variabilis Ad. and Ang. P. Z. S. 

 1864, p. 194, probably belongs to this genus, but has not been 

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

 of insertion teeth ; and from Placiphora by the regular articulation 

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

 pores, Angasia will represent Chcetopleura in the tufted series, as 

 Callistoplax represents Callistochiton. " 



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 (Q?r.) 



Ceylon (Mus. Cuming, No. 83). 



A. tetrica CPR. MS., and in BALL, 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. The same 



