B :^ m i^ m n m am m c^so) 



Fam. 8. CYRENIDAE. 



m A m m n 



291. Cffvenn liichuana Pils. 



C. M. M. J., p. 183, pi. 9, f. 4, 5. 



Nom. Jap. Shirena-shijimi (Iwak.). 



Dist. Kagoshiina (1515) ; Eiukiu (1516) ; Yaeyama (1517). 



292. Cfjrena Jissidens Pils. 



Ibia.,pl. 8, f. 5,6. 



Nom. Jap. Do. 



Dist. Yaeyama (Stearns). ■ 



293. Vyrena i/aej/ntnensis PiLS. 



Ibid., pi. 9, f. 6. 



Nom. Jap. Do. 



Disfc. Do. 



The above three are at present the cnly species of our Gijrena. 

 Dr. PiLSBRY, who had firstly described them with the specimens 

 from Yaeyama collected by Stearns, has divided them into three 

 species as above cited, — luclmana, jissidens and yaeyamensis. 

 Having closely exinainad many individuals of the same species from 

 the same localit}', anl referred to the diagnoses as well as the figures 

 given by him, I have inclined to think that the distinctions of the 

 three species are merely due to the different ages of the shells. 

 In my opinion, Pilsbry's yaeyamensis is considered to be the 

 youngest, lucJmana the adult, and fissldens an intermediate form, 

 which is rather rare, there being only two among my fourteen 

 individuals ; about the rarity of this form, he also says that be 

 has found only a single specimen among many individuals. The 

 probability that the distinctions of these species are owing to the 

 age of shell can easily be recognised from the sizes of the shells 

 measured by Dr. Pilsbry and myself, viz. — m 



yaeyamensis L. 75, B. 63, D. 36 mm. 

 fissldens ,, 86, „ 77, „ 49 ,, 



luchuana „ 94, ,, 72, ,, 47 ,, 



