28 Bastotv and Gatliff: 



creamy ansrular markings at each side of the dark well-defined 

 dorsal trianpnlar area. Girdle alternating blackish browD and 

 creamy, with radiating separated scales. 



In perfect specimens the mediaai valves are beaked, and are 

 covered over their whole surfaces with small granulated pustules, 

 for the most part in longitudinal and transverse lines, the diaigo- 

 nal rib not showing very plainly. The triangular patch of colour 

 on the dorsal ridge is evident on all the specimens examined. 

 The anterior vaive is pustulated over the whole surface in a 

 concentric manner ; the anterior portion of the posterior valve 

 is radially pustulated, and the posterior part is similar to the 

 median valves. 



The interior is considerablj* coloured brownish purple, and the 

 surface finely laminated ; the sinus is broad and denticulate ; 

 the anterior valve has ten slits, the teeth are long, deep, sharply 

 and closely pectinated outside; the median valves have one slit; 

 there are no slits in the posterior valve, but the posterior edge 

 is strongly denticulate. 



The girdle is tough and fleshy, difficult to remove, bearing 

 numerous wide, blunt, striated, separated scales ; in the inter- 

 stices are a few scattered spines. 



The head-valve is studded with numerous bright, clear, amber 

 eyes, not ocelli, but real and very human-looking eyes ; these 

 also occur on the lateral areas and on the posterior valve. They 

 have optic nerves which can be traced by slightly decalcifying 

 the valve and thus making bare the eye orbit ; the nerve threads 

 pass from the eyes to the mantle of the animal, as may be de- 

 tected by breaking away the teeth fi-om the ventral surface of 

 the anterior valve, the outlets of the nerve threads are then 

 revealed in the caves, just under the tegmentum, and from 

 thence, Mr. Pilsbry informs us, they are connected to the central 

 ganglion. There are also numerous punctures on the venti'al 

 sides of the valves, and a multitude of megalopores and micro- 

 pores visible as very narrow granulated striations over the 

 pustules of the dorsal areas (Fig. 3) with chambers embedded 

 in the shell; these are all similarly connected; it is probable 

 that these latter are also nerve channels for tactile, auditory, 

 or other sense organs. The girdle, with its radially striated 



