502 KOTES ox AUSTRALIAN SHIPWORMS, 



anterior area is crossed by close, delicate, most regular lamellae, 

 about a quarter of a millimetre apart ; at right angles to these 

 unite a series closer together and finely beaded on their umbonal 

 aspect, which traverse the antero-median area parallel to its 

 margin ; on reaching the median area the sculpture loses its 

 regularity, is deflected backwards and upwards, degenerating into 

 vague strise parallel to the margin of the posterior area. The 

 auricles with part of the posterior and the whole of the umbonal 

 region are too much eroded to exhibit sculpture. 



Viewed from within, a prominent feature is the thin, flat 

 apophysis which projects from the centre of the subumbonal ridge 

 into the cavity of the shell for half the latter's length, its jagged 

 edges parallel to the axis of the valves. From the apophysis to 

 the posterior auricle the subumbonal ridge stretches as a shelf 

 into the cavity of the valve. Along both anterior and posterior 

 margins the shell is reinforced from within by a heavy layer of 

 callus. Beyond the ventral tip each valve has projecting from 

 within a little peg of callus, which is slightly excavated at its 

 upper end. Hinge tubercles spiral, swollen, large, projecting 

 downwards and interlocking each to each by spurred processes. 

 Anterior adductor muscle scar covering most of the interior of the 

 anterior area. Height 25, length 22, breadth 26 mm. 



Palettes somewhat the shape of a cricket bat whose shoulders 

 had been planed down ; stalk with two notches at the end, from 

 the lower of which runs a groove to the ring that marks the com- 

 mencement of the blade ; the latter a little concave within and 

 convex without, shelly and like a Sepia shell for two-thirds of its 

 length, membranous at the end. Length 27 mm. Breadth 6|-. 

 This feature <fig. 5) ill corresponds with that drawn on Tate's 

 plate, which rather approach the palettes of Knphus (as illustrated 

 on PI. Lxv. of Vol. XXV. of the Trans. Linn. Soc). 



As my sketch (PI. xxxii. fig. 4) indicates, the tube of the species 

 under discussion is for some distance partially choked by a series 

 of imbricating plates. 



From most species of its genus, this, one of the largest, is 

 separated l>y the almost entire suppression of the auricle, in which 



