FOSSILS FROM TUE ENVIRONS OF TOKYO. 91 



Rifusiri, Koix'ii, I'ossjot Hay, Castries Jîay, Cape Notoro, Caj)e Tofiits, 

 lAninosa, Sini^^apore, China, East Indies, New Zealand, Java, 

 Anihdina, l\L:ypt, ]>rituin, Mediterranean, I-'ranee, rvrenncse 

 Peninsula. 

 * Modiola modiolus Linn. — Tokyo, Hakodate, Hetouchi, Beiiring- Sea, 

 Lapland in Russia, entire North Atlantic Coast of Europe ar.d 

 America, and New England in America, ^liditerranean Sea. 



As may be seen from the above list, in which species 

 marked witli asterisks are those found also in our fossil locali- 

 ties, the number of tropical Ibrms found living and in the fossil 

 state is quite small. Tlie tropical living species amount to 399^ 

 of the whole, wliile the arctic amount to 4^0, and those found 

 only iu Japan to ô')^o. Eut the percentage in our fossil forms 

 is as follows : 



Troi)ical species 22 fo 



Arctic species 15 ?o 



It is quite interesting to observe that, while the proportion of 

 the arctic to tropical species in the list of the above ]ivin<>- 

 fauna is 1 : 9.75, that of the fossils is 1 : 1.4(). 



Among the fossil forms, the following are not found in the 



environs of Tokyo : — 



Neptunea despecta LissL—Buccinum undatum Linxé. — Natica clausa 

 T>K<n.—Panopœa generosa Old. — Mactra sachalinensis Sciikexck.— 

 Venus stimpsoni Cld. — Tapes rigidus Ghw—Astarte Japonica ïok. — 

 Tapes euglijptus Pn. — Martesia striata Linné. — Lueina horealis L. 



These species are never found in tropical regions, and the ßrst 



eight species are restricted to arctic fauna. From this we see 



that the sea near Tokyo was formerly inhabited by univalves and 



bivalves of a climate colder than that which prevails at present. 



Next let us consider the question of the geological age 



of our fosteil beds. Era uns assumed the existence of a line of 



unconformability between the shell bed and the Diluvium above 



it, and identified manv of the shells with those of the Ensflish 



