Art. 1. — M. Yokoyama : 



■fhe left valve tliere are two diverging eminences, with a triangular 

 ligamental pit behind, divided into two parts by a median 

 ridge; the right valve has but one tuoth. Palliai sinus shallow, 

 crescentiform. Not rare. 



The following are the measurements: 



Length. 

 12.5 millim. 

 10 2 



Left valve 

 Eight „ 



55 55 



Fossil occurrence. — Shito. 



10.3 

 11.0 



Height. 



9.3 millim 



7.4 „ 

 7.6 „ 



8.2 ., 



Depth. 

 4.0 millim. 

 8.0 „ 

 3.0 „ 

 3.3 „ 



Family Modiolidae. 



G-enns MOOIOIiA, Lamarck. 



2S2. Modiola harhatii, (Linné). 

 PI, XIV, Fig. 19. 



Modiola barbata. Forbes aud Hanley, Brit. Moll., II, p. 190, pi. XLIV, tig. 4. Pils- 



bry, Catal., p. 140. Wood, Crag Moll., Biv., p, 58, pi. VIII, fig. 2. 

 Mytiliis barbatus. Linné, Syst. Nat., Ed. 12, p. 1156. Jeffreys, Brit. Conch., II, p. 114. 



Only young shells. The largest is a left valve still preserv- 

 ing a little of the original reddish brown colour. It is ovately 

 triangular in outline and obtusely pointed at the smaller and, with 

 the ventral margin somewhat excavated. ïlie other specimens 

 which are all younger have a more posteriorly expanded sliape, 

 though, compared with the Crag form, the posterior expansion 

 as well as the ventral excavation is less. Anyhow there is a great 

 variation in outline as is evident on examining the specimens of 

 the recent shell. 



The greatest extension of the largest specimen above referred 

 to is 11.8 millim., while the dimension across where it is greatest 

 is 6.3 millim. The depth is 2.8 millim. There is also a smaller 

 left valve 7.1 millim. long, 4.8 millim. broad and 2 millim. deep. 



Fossil occurrence in Japan, — Tega (very rare), Otake (do), 

 .Shito (rare). Oji in Musashi. 



