ANATOMY AND LIFE HISTORY OF MOLLUSCA. 175 



plays a very important part, and it is here that the dermal eyes 

 must be looked for if they exist at all. This, however, is the 

 part that is ruthlessly swept away by the shell collector, and a 

 most important and interesting portion of the animal organism 

 is destroyed. It is thus, as I have already stated, that the 

 shell-eyes of the Mollusca have remained so long concealed from 

 naturalists. 



Cerithium ebeninum, Brug. — In the mantle of this species I 

 have discovered curious rounded bodies having all the appearance 

 of eyes enclosed in semilunar chambers, at the extreme edge of 

 the mantle which is also studded with innumerable minute rounded 

 bodies which refract the light very brightly. These larger bodies, 

 possibly, are compound eyes, and together with the smaller 

 bodies, are reserved for special examination. The whole of the 

 mantle is interlaced with nerve-fibres and a few capillary channels. 

 There is always a distinct and abundant nerve supply at the base 

 of these mantle-eyes. Outside the thickened margin of the mantle 

 there is an excessively thin membrane which stretches beyond it. 

 (For figure of shell see pi. v., fig. 5.) 



Acmcea marmorata, Tenison- Woods. — Sense-organs in the form 

 of little black dots surrounded by a darkened ring. Perhaps in 

 the whole extent of a shell there may not be more than one or 

 two such clusters containing about 20 eyes. (?) 



Emarginula rugosa, Sowerby. — This species has prominent ribs 

 which the transverse lines of growth divide into nodules of irregular 

 size. The sense-organs are very numerous in some species, possibly 

 on all, but they are so small that they are very difficult to see. 

 Like all shells with a rough exterior, there is always an abundant 

 growth of algae and shelly parasites where of course the shell 

 structure is destroyed. 



Trochocochlea tceniata, Q. <fe G. — Sense-organs very minute, in 

 little darkened pits, crowded irregularly over the whole surface of 

 the shell. Cornea (?) very brilliant and where the organs project a 

 little it seems as if the shell were studded with gems. Underneath 

 the tegmentum of this shell, the next shell-plate is completely black 

 and apparently full of little foramina for the passage of nerves 

 and blood-vessels. 



Venus paucilamettata, Dunker. — This is a somewhat common, 

 thick, opaque shell, about 1J inches in transverse diameter. The 

 substance is very opaque and only permits the structure to be seen 

 in the thinnest sections, and then indistinctly. The surface is 

 covered at intervals, not entirely, with sense-organs, forming a 

 close pavement of minute capsules, so small as to make it impossible 

 to see their structure unless with very high magnifying powers. 

 The capsules, however, contain nerves. This species can only be 

 •examined to advantage in the freshest specimens. The calcareous 



