Iß4 Art - 6.— M. Yokoyama : 



Area ocellata. Kobelt in Syst. Conen. Cab. Mart. u. Chemn., vol. "VIII, p. 87, pl. 24, figs. 

 1-4, (non Eeeve). Pilsbry Cat. Mer. Moll. Jap., p. 148. 



Area reetangularis. Toednaga, Foss. Env. Tokyo, p. 61, pl. Ill, fig. 23. 



The shell is generally transversely quadrate, very convex 

 with the posterior margin obliquely truncate, so that it makes a 

 blunt angle with the straight or even concave ventral margin. A 

 sharp keel runs from the beak to the postero-ventral corner. The 

 surface-sculpture consists of numerous granulated, subequal, radia- 

 ting ribs which on the posterior side become larger and often double 

 and are separated by wide interspaces with a few (generally two) 

 small riblets. The surface is more or less uneven, so that the ribs 

 are also somewhat undulating. 



Pilsbry lays great stress on the character of the area as a dis- 

 tinction from Reeve's Area ocellata, and speaking of his Area Tco- 

 beltlana, he says. 



,, The wide ligamental area is marked off into concentric 

 lozenges by very numerous ligament-filled, diagonal, broadly v- 

 shaped sulci, of which I count 11 in a shell 44 millim. long, 

 17 in one 55 millim. long. The hinge-line is narrow, the teeth 

 fine, close and vertical in the middle, somewhat irregular there and 

 anteriorly, but posteriorly they become coarse and very oblique 



and strongly crenulate on the upper edges Having before 



me a topotype of Area ocellata Rve as well as several Japanese 

 specimens which agree with them, I am compelled te regard the 

 two species as entirely distinict, and not even closely related, al- 

 though they agree in general shape. The ligamental area in 

 A. ocellata is smooth, scored by only a few, usually imperfect 

 ligament-grooves, there being a large oblique triangle posteriorly 

 and an erect triangle between the beaks free from them. The tw r o 

 oblique triangles marked by grooves are usually- covered with a 

 smooth yellow (or in some Japanese shells, blackish) cuticle, while 

 the rest of the area is whitish. This is well shown in the dorsal 

 aspect of a specimen of A. ocellata from the province of Suruga 

 drawn in fig. 21 of pl. XLI. " 



In fact all of our fossil specimens have lozenge-shaped grooves 

 crossed by lines parallel to the hinge-line, whose number varies 



