27 



party made exhaustive collections by dredging, and shore collecting, at various 

 points along the coast at Kishiu, yet foiled to secure a single specimen. 



Lischke in his great work, Japanische Meeres Gonehylien, records examples from 

 Nagasaki only. He gives the following localities : Tochi-fu, North China and 

 Cochin China, Debeaux ; Philippine Islands, Reeve ; Ceram and Celebes, Rum- 

 pJdus ; Tran quebar and Nikobaren, Chemnitz. E. E. C. Stearns Esq. of the 

 University of California says that the Mound specimens have a loss number of 

 ribs ; — the species at present having from 23 to 26 ribs, while the Mound speci- 

 mens range in number of ribs from 1 8 to 20. 



Mr. Stearns further remarks that the Mound specimens differ from the present 

 form in being less equilateral, and in having the umbones less produced. He says 

 it is at present a southern form, and belongs to a widely separated geographical 

 province. 



In the digging of wells in Tokio it is often brought up in a semi-fossil condi- 

 tion from considerable depths. I have also found it in great numbers in an 

 ancient mound in Tokio proper, associated with pottery and rude stone imple- 

 ments, and Mr. Ishikawa has found it associated witli cord marked pottery 

 beyond Oji. From these evidences it must have been a common shell in past 

 times, but has now become extinct in this and neighboring waters. ■ 



Lischke gives the following measurements of two specimens from Nagasaki, 

 and one from Singapore. 



Length. Hight. 



Nagasaki, 54 40 



„ 44 HI 



Singapore, 32 28 



Largest specimen from the Mound 57 42 



Average of ten largest specimens from the Mound, .32.0 41.1 



It is interesting to observe that the two other, species of Area from the Mound 

 possess a less number of ribs than the present species. In other words the three 

 species of Area at the present time differ in possessing a larger number of ribs 

 than their ancestors, beside the other differences already recorded, as follows : 



Mound. Eecent. 



I Area sub-erenata, 30.5 33.3 



Number of ribs in, ., inflata, 39.6 41.2 



I „ granosa, 18 to 20 23 to 26 



Cyclina CMnensis Chemnitz. Plate xvm. Fig. 1. 



This species is not common along the shores at Omori. Lischke records a 

 single example from the Bay of Yedo, and thirteen from Nagasaki. I have a 

 number of specimens from Omori village. 



