Xyn ^^^- !• — ^' Yokoyama : 



on the right only on thoF^e near the anterior end of the shelh A 

 fuller account is found in the work of Yamakawa above cited. 



Fossil occurrence. — Otake (very common), Kioroshi, Kame- 

 nari, Shisui (common), Tega (very frequent), Shito (rare). Oji. 



Living. — Central, Western and Southern Japan. 



Genus PFX'TUNCTItUS, Lamarck. 



315. JPecfunculus albolitieafus, Lischke, 



PI. XVn. Figs. 1, 2, 3. 



Pcctunciihis alholineatits. Lischke, Jap. Meeresconch., Ill, p. 108, pi. IX, figs. 11, 12. 

 Duiiker, Ind. Moll., p. 236. Brauns, Cleol. Euv. Tokio, p. 45. Toknnaga, Foss. 

 ]<:iiv. Tokyo, p. 61. Pilsbry, Cat., p. 150. 



Lischke who first described this species had only young shells 

 of a more or less circular form whose length was below 40 millim. 

 But there are specimens which are 80 millim. long. Such full- 

 grown ones are not circular, but decidedly somewhat obliquely 

 round-squarish, the antero-dorsal corner in front and postero-ventral 

 corner behind being most produced. Such a squarish form we 

 can also find among the j^oung shells in wliich, if not both corners, 

 at least the antero-dorsal corner is more or less produced. From 

 this it is quite certain that there is a great variation in the outline 

 of the shell. The surface ornamention consists of white radiating 

 lines and fine dots. 



The fossil specimens which I deem as belonging to this species 

 are a few isolated valves which ai-e quite grown. They are also in 

 general roundly squarish, but the posterior margin is a little more 

 rounded than in the recent shell, so that the protrusion of the 

 postero-ventral corner is not so obvious. One of the left valves 

 measures 08. 6 millim. in length, 59.5 millim. in height and 17.8 

 millim. in depth, while one of the right measures 68 millim. in 

 length, 56,5 millim. in height and 17.2 millim. in depth. 



The surface-dots are obliterated in the fossil and the white 

 radiating lines are present as impressed ones with several finer 

 interstitials between. 



