29 



Assuming length to be 100, night in ( 10 g S P e ™ s ' g»»£ »jg 



Length. Hight. 



D. <. i . • ( Recent, 68. 63. 



lmensions oi largest specimen, , r ,' _„ _ „., 



01 ' Mound, 7 i.5 7->. 



Maetra venerformis Deshayes. Plate xvm. Fig. 3. 



This sjtecies is very common in the Mounds, and along the shores of the Bay. 

 It is also common iu the markets of Tokio. Lischke gives the average size of 

 the species as follows : length 38, hight 34. 



He also gives the dimensions of a specimen from Kishiu as follows : length 

 48, hight 44. 



The following are the dimensions of the Mound specimens iu comparison with 



the recent at Omori. 



Length. Hight. 



Average dimensions of ( Recent, 43.4 38.1 



ten largest specimens, { Mound, 56.6 49.1 



Assuming length to he 100, hight in f ?£ Jj?<» n J. 88.3 

 00 ' ° I 15 Mound, 8b.b 



Length. Hight. 



T-.. . e , , . f Recent, 48.5 43 5 



Dimensions oi largest specimen, J -vr j ?o ri .- 



It will he seen by the above figures that the average hight of the Mound shell 

 exceeds the length of recent specimens as given by Lischke, and is much longer 

 than the shell as it exists to day at Omori. Its proportions have moreover 

 changed. 



Cytherea meretrix Linne. Plate xvm. Fig. 7. 



Under this name Lischke probably refers to the species to be considered. It 

 is one of the principal shells iu the Mounds and appears equally common along 

 the Omori shores. 



The proportionate diameters vary but little, but the difference in size is notice- 

 able at once, the Mound specimens being larger. 



Length, Hight, 



Average dimensions of ( Recent, 85.8 66.1 



ten largest specimens, ( Mound, 97.3 75.1 



