Fossils from the Miura Peninsula, and its Immediate North. 7] 



Family Vermetidae. 



Genus Thylacotles^ Guettard. 



68. Thylacod.es medusae, Pilsbry. 



Pl. IV. Fig. 7. 



Thylaeodes medusa. Pilsbry, Proc. Acad. Nat. Sei.. Philad., 1891, p. 471, pl. 17, 18. Cat, 

 Mar. Moll. Jap., p. 59, pl. IV and V. 



This species is characterized by Pilsbiiy as having "narrow 

 longitudinal cords at rather wide intervals, the spaces between 

 being, occupied by a variable number of threads, (usually three) of 

 which the middle one is the largest." And this sculpture is 

 normally "developed upon all sides of the tube," though upon 

 the latter part of the free portion it is often subobsolete." The 

 cross-section of the adult tube is circular. Rather frequent, though 

 mostly in fragments. 



Fossil occurrence. — Miyata Zone (Shimo-Miyata); Yokosuka 

 Zone (Yokosuka). Upper Musashino of Kazusa, 



Living. — Central Japan (Suruga). 



Family Turritellidae. 



Genus Turritella* Lamabck. 



69. Turritella nipponica, Yokoyama. 



Pl. IV. Figs. 16-19. 



Shell high-tun etc; whorls numerous, nearly Hat, slightly 

 angulated a little above the sutures, spirally ribbed; ribs normally 

 five, one which is suprasutural being usually not prominent except 

 on the body-whorl. Of the four upper ribs, the lower two are 

 stronger than the upper two; the two stronger ones of which the 

 lower forms the angle generally Hat-topped, while the two weaker 

 ones are usually sharp and ridge-like, though sometimes they may 

 also be flat-topped. In abnormal cases, the number of ribs may 

 altogether be six instead of five (either the stronger or the weaker 

 ribs becoming three), in which case the weak suprasutural one 

 may also become prominent. The spaces between the ribs are 

 either smooth or spirally striated, the striae often appearing also 



