Note on the Eyes of Cardium Muticum Beevel 

 K. Kishinouye, Riéakushi. 



Zoologist to tlie Department of Agrienltnre and Commerce. 



Witli Plate IX. 



The eyes of the genus Card! um have been studied by many 

 authors; but. so far as I know, no one has yet found such conspicuous 

 eyes as I describe below in the molhiscs of this genus. The following 

 note may therefore ])rove interesting to investigators of the molluscan 

 eye. 



The mnntle-edges, both right and left, of Cardium muticum are 

 beset witli dnrk brow^n. almost black pigment. They unite at the 

 posterior end of the shell and form a triangular pigmented area, sur- 

 rounding the siphon;« 1 openings. Over this area the right and left 

 valves of the shell do not meet closely but leave a rathei" wide slit. In 

 this triangular, pigmented area w^e find a, great many tentacles, ar- 

 ranged in many irregular rows round the siphonal openings. 



The tentacles are of \'arious sizes : those on the peripliery of the 

 pigmented area are larger and longer; tliose towards the siphonal 

 openings, shortei- and more sleîider till at the margin of these 

 they are reduced to mere fringes (fig. 1). Clenerally speaking the 

 larger and longer tentacles about 100 in number bear the eyes. They 

 are bent away from the siphonal openings, and eacli of them has a 

 longitudinal band of black pigment on the siphonal side, 7. e. on the 



