Mr. A. Adams on Japanese Mollusca. 363 



tlie longest, twice as long as thej are wide. The last joints 

 slightly compressed, smooth; the last has a strong tooth 

 besides the final hook. The first joint of the arms, arising 

 direct from the knob of the calix, bears a pinnula immediately 

 and has a syzygium ; the second is without a pinnula ; the 

 third bears one ; and the fourth has a pinnula, and also a 

 syzygium. Then the pinnulse succeed each other, alterna- 

 ting regularly, and always one syzygium between 3-5 joints. 

 The joints of the arms are nearly twice as long as they are 

 high, and, especially in the centre, are strongly wedged 

 sideways. The first two pinnulae are small, the third and 

 fourth the longest ; then follow shorter ones, which, towards 

 the end of the arms, gradually become longer and thinner, 

 whilst the first issue with rather a broad basis. Length of 

 the arms 80 millims., of the cirrhi 9 millims., of the longest 

 pinnulae 8 millims ; the diameter of the central knob is 2 

 millims. 



Unfortunately the disk is missing in the single specimen. 

 The pinnulge are speckled over with light and dark yellowish 

 brown ; the back of the arms is marked by two winding lines. 



Pandanon, near Bohol (Philippines), at a depth of 30 

 fathoms. 



XLIV. — On the Species of Caecid^, Corbulidae, Volutidae, 

 Cancellariidge, and Patellidaeyoww^ in Japan. By Arthur 

 Adams, F.L.S. &c. 



Pursuing my investigations into the molluscan fauna of the 

 Japanese Islands, I have in this communication to identify, 

 enumerate, and systematically arrange the species of some 

 families of which our knowledge in respect to geographical 

 distribution was formerly somewhat limited. With regard to 

 those curious but minute creatures, the Cceca^ it appears strange 

 that I should have met with no new species. As to such a 

 littoral family as Patellidae, it is not singular that all the spe- 

 cies should have been previously known, as casual observers 

 and sailors are pretty sure to collect them. These shore- 

 inhabiting species are subject to very great variation ; and the 

 chief difficulty in dealing with them consists in disposing of 

 the varieties into groups which are natural, so as to reduce the 

 number of the so-called species. All the localities are given 

 solely on my own authority. Numerous other families still 

 remain to be worked out before we can arrive at even an ap- 

 proximate knowledge of the Mollusca of Japan. The speci- 

 mens forming the material from which this enumeration has 



