Fossils from the Upper Musashino of Kazusa and Shimosa. 147 



Genus SU NETT A, Link. 



2»1. Suneffa eoceavafa (Hanley). 



PI. XI. Fi^'s. 6, 7, 8. 



■Sunetta e.vcacata. Adams, Gen. Eec. Moll., II, p. 428. Pfeiffer, Syst. Conch. Cab., XI, 



pt 1 p 83, pi. XXIX, fig. 4. Dunker, Ind. Moll. p. 201. Pilsbry, Cat., p. 127. 

 ■Crjtherealvcacata. Hanley, Proc. Zool. See. Lend., 1842, p. 123, Descript. Cat., p. 



109, pi. 15, fig. 19. 

 Meroe e^ccamta. Sowerby, Thes. Conch., II, p. 610, pi. 126, figs. 13, 14. Eeeve, Conch. 



Icon , Meroe, pi. Ill, fig. U- Lischke, Jap. Meeresconch., II, p. 110. 

 Sunetta memtraalis. Römer, Monogr. Venus, II, p. 13, pi. IV, fig. 2. Pfeiffer, Syst. 



Conch Cab., XII, pt. 1, p. 85, pi. XXIX, figs. 10, 11, 12. Pilsbry, Cat., p. 127. 

 C^Jtherea menstnudis. Menke, Moll. Nov. Holl, sp. 43. Philippi, Abbild., II, p. 96, no. 



3, Cytherea, pi. IV, fig. 3. 

 mroe menstruaUs. Sowerby, Thes. Conch., II, p. 742, no. 8, pi. 163, fig. 17. Reeve, 



Conch, Icon , Meroe, pi. Ill, fig. 9. 

 mwe matjnißca. Eeeve, Conch. Icon., Meroe, pi. I, fig. 2. 



Lischke unites the two species of Sunetta excavata Hanley and 

 Sunetta menstrualis Menke into one, and quite rightly. I have a 

 few large specimens which are typical Sunetta menstrualis and 

 many small ones which can l)e assigned to .S'. excavata. The 

 former are up to 57 miUim. in length, roundly oval in form, 

 compressed and rounded at both ends, the anterior more sharply 

 than the posterior, while the latter are more oblong or eUiptical 

 in shape, with the posterior end mostly truncate or subtruncate 

 and smaller in size, usuahy being less than 20 miliim. in length. 

 But on examining the young specimens of the living shell, I was 

 convinced that the form graduahy passes from the one into the 

 other, so that there is no reason for separating the two. 



Pfeiffer in ' ' Systematisches Conchylien-Cabinet ' ' above cited 

 mentions the fine radiating lines of Sunetta menstrualis as one of the 

 distinctions from the other species, but as such lines are very 

 indistinct in young specimens, they can not be of much value in 

 distinguishing the two. 



The largest left valve measures 57.1 milhm. in length, 47.2 

 milhm. in height and 10.5 milhm. in depth, while the largest 

 right measures 54.3 milhm. in length, 45 miliim. in height and 

 9.5 miliim. in depth. 



