72 Art. 6.— M. Yokoyama;.. 



un the ribs themselves. On the body-whorl below the angle-rib, 

 there are a few spiral ribs often with interstitial spiral strias. Base 

 rlatly convex. Aperture roundish. 



The specimens are mimerons, but the adult ones are mostly 

 broken, so that it is very difficult to ascertain the number of 

 whorls. But judging from the more perfect younger ones, they 

 must have been at least fifteen. The largest specimen measures 

 about 14 millim. in diameter. The height of such specimens 

 might be estimated at about 60 millim. i 



This species is related to Turritella facialis Menke (Tryox. 

 Man. Conch., vol. «S, pi. 51), figs. 3C>, 37) which is, however, four- 

 ribbed. Turritella bacillum Kiener (Tryox, pL 59, figs. 34, 35) 

 which is also akin to our species has six ribs and convex whorls. 



Fossil occurrence. — Miyata Zone (Kami-Miyata), rare; Kana- 

 zawa Zone (Nojima and Kanazawa), very frequent; Koshiba Zone 

 (Koshiba), also very frequent; Nnganuma Zone (Naganuma and 

 Sugita), rare. 



Family Solariidse. 



GeilUS Solarium, LiAMARCK. 



70. Solarium lenticulatura, Yokoyama. 

 Pl. IV. Fig. 21. 



Shell small, lenticular, rather solid; spire very rlatly conical; 

 whorls about five, somewhat convex, spirally striated; striae about 

 six on the penultimate whorl, unequal, the lowest one close to the 

 suture being the largest, with .a shallow, but comparatively wide 

 furrow between this lowest and the next one; in this furrow there 

 is a fine spiral line which may grow into the size of the other 

 strirc, in which case, the furrow becomes more or less indistinct. 

 Lines of growth coarse, their points of intersection with the stria^ 

 being more or less granulated. Periphery angulate, and finely 

 crenulate. Base convex, outer half with several spiral striae, 

 inner half with very coarse growth-lines which appear like radiat- 

 ing striae. Umbilicus large, deep, with margin crenulated, sur- 



