Fossils from the Miura Peninsula and its Immediate North. I4.K 



183. Mytilus giganteus, Holmbebg. 

 Pl. XT. Fig. 20. 



Mytilus giganteus. Lischke, Jap. Mi en si on '., I. p. 150. 



Mytilus edulis forma gigantta. Axes, von Sordmann, Ball. Soc. Imp. des Naturalistes de 

 Moscou, 1862, p. 422, pl. XI, XII. 



The fragments of a large -shelled Mytilus, all belonging to the 

 beak-portion. That these belong to Mytilus giganteus is shown by 

 numerous small pits covering the whole inner surface of the shell. 

 A species described as Mytilus ungulatus Lam. by Schrenck from 

 Northern Japan may possibly be the same species, as already 

 pointed out by Lischke. 



Fossil occurrence. — Yokosuka Zone (Ofcsu). 



Living. — Northern(?), Central and Western Japan. Also 

 near Sitka in Alaska. 



Genus Modiola, Lamaeck. 



184. Modiola modiolus, Linné. 



Pl. XL Fig. 21. 



Modiola modiolus. Linne, Syst. Nat. ed 10, p. 706. Lischke, Jap. Meeresconch., I, p. 156, 

 II, p. 147, JII, p. 109. Dunkeb, Index Moll. Mar. Jap., p. 222. Tokunaga, Foss. Env. Tokyo, 

 p. 63. Wood, Crag Moll., Bivalves, p. 57, pl. VIII, fig. 1. Nyst, Conch. Terr. Tert. Belgique, 

 p. 163, pl. XVII, fig. 5. 



Modiola grandis. Philippi, Ennui. Moll. Sic., vol. II, p. 51, pl. 15, fig. 13. 



Several large specimens measuring up to 95 millim. in length. 

 Compared with recent forms from Hakodate, they are more 

 parallel-sided in the posterior portion, and their posterior margin 

 is a little more subtruncate, looking like a specimen represented 

 in Reeve's work (Conch. Icon., Modiola, pl. I, fig. 2). 



Fossil occurrence in Japan. — Miyata Zone (Matsubara in 

 Shimo-Miyata). Upper Musashino of Kazusa. 



Fossil occurrence in foreign countries. — Crag of England; 

 Pliocene of Belgium and Italy. 



Living. — Northern, Central and Western Japan; North 

 Pacific; North Atlantic. 



