Fossils from the Upper Musashino of Kazusa and Shimosa. 189 



Fossil occurrence. — Otake. Oji. 

 Living. — Central Japan. 



U16. Pectunculus vesfitiia, Dunker. 



PL XYI. Figs. 1, 2, 3. 



FectuncuUs vestitus. Dimker, Ind. Moll , p. 230, pi. XYI. figs. 7, Ö. Pilsbry, Cat., p. 



150. 

 Fectunclm rotnndus. Dunker, Ind. Moll., p. 236, pi. XVI, figs. 7, 8. Pilsbry, Cat., 



p. 150. Yokoyama, Foss. Miura Peniu., p. 167, pi. XVII, figs. 10, 11. 

 This species shows a great vnriation in the outhne of the shell. 

 The normal form is a rounded oval, slightly ohlique, somewhat 

 longer than high and witli the beak-portion narrowed. What 

 Dunker gives in his figure (pi. XVI, figs. 7;8) is a less rotund form 

 with the length somewhat greater than in the normal type. 

 Young examples of this shell which can be collected in hundreds 

 at some localities are more circular in form, and it is quite certam 

 that Bunker's Pectunculus rotundus is a species founded on such 

 examples. It is here to be noted that among the adult ones there 

 are often forms which possess the more produced and subtruncate 



posterior end. 



The surface in recent specimens is ornamented with white 

 radiating lines as in the preceding species, which are present in the 

 fossil as impressed Unes with finer ones between. But the dots of 

 the latter seem to be absent. Therefore the young circular form 

 of the preceding species, when the dots are obliterated, is difficult 

 to distinguish from the present. 



The largest specimen in our collection is a right valve 76 

 milhm. long and 68.5 millim. high. 



Fossil occurrence.— Otake (numerous), Kioroshi (do), Kame- 

 nari, Tega (numerous). Tabata and Shinagawa. Lower Musashino 

 of Miyata and Naganuma. 



Living. — Central Japan. 



S17. JPeetu^tetiltts yessoensis, Sowerby. 

 P]. XVI. Fig. 6, 7. 

 Pectmculus yessoenm. Sowerby, Descr. Fourt. New Shells fr. Cbiim, Jap. a. Andam. 



