560 PLEUROBRANCHIDi^:. 



very much stronger, the substance being shelly. It is of a 

 lighter or darker glossy horn colour, generally tinged with 

 yellow, especially on the polished interior, and usually dis- 

 plays rather conspicuous wrinkles of increase. The shape 

 is oblong, slightly broader and somewhat squared above 

 (though the angles are rounded off), and rather bluntly 

 rounded below ; the sides are subparallel, but the outer lip 

 is much more arcuated above, and becomes retusely in- 

 dented below the middle, after which it bends convexly to 

 the anterior extremity. Two or three impressed lines 

 obliquely radiate, upon the exterior, from the outer corner 

 of the lower extremity towards the crown, which latter 

 exhibits a perfectly distinct, though minute, spiral coil. 

 When the aperture (which displays the whole interior, 

 there being merely an extremely narrow lateral convolution 

 above) is placed on a flat surface, the shell rests solely on 

 its upper and lower extremities (as in Parmophorus, of 

 which genus it forcibly reminds us), leaving a slight but 

 extended gape in the middle : hence, although the shield is 

 depressed, it appears rounded on the back. The pillar lip 

 is very narrow, but is decidedly reflected. Our largest 

 specimen, which is about twice as long as it is broad, 

 measures about three-fifths of an inch from the top of the 

 outer lip, which projects slightly above the crown, to the 

 opposite extremity. 



The animal is, when at rest, of a suborbicular shape, 

 when creeping it is oblong. The dorsal disk is convex, 

 smooth, yellowish-white, and speckled with reticulating 

 whitish dots : the shield shining of an orange colour 

 through the skin, which is strengthened by spiculae. The 

 tentacula are rather long, their bases, with the minute eyes, 

 are hidden beneath the margin of the mantle. The foot 

 extends beyond the dorsal disk, and both have a slightly 



