32 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 06 



Otaru, Japan; University of Tokio. Collected by Prof. E. S. 

 Morse. 



This species compared with T. johanni is more equilateral, more 

 completel}^ and much more strongly obliquely sculptured and, when 

 full grown, larger. 



YOLDIA (CNESTERIUM) JOHANNI, new species 

 Plate 29, fig. 7 



Shell olivaceous, compressed, inequilateral, equivalve, polished, 

 smooth except for incremental lines and fine oblique rather w^idely 

 spaced striae which occupy the middle part of the disk, stopping 

 abruptly at about the anterior third and leaving a smaller space near 

 the posterior end also vacant ; the beaks are inconspicuous, the lunular 

 area is compressed and vertically produced, the anterior slope nearly 

 straight, the posterior end slightly rostrate and recurved, the basal 

 margin evenly arcuate; there are about 16 posterior and 32 anterior 

 hinge teeth, the ligament rather large and strong, the pallial line 

 with a large rounded free sinus; total length, 30; the beaks in front 

 of the posterior end, 12 ; altitude at the beaks, 13.5 ; diameter, 5 mm. 

 U. S. Nat. Mus. Cat. No. 107694. 



North Japan, in 7 fathoms, Captain St. John, R, N. 



This belongs to the same group as Y. seminuda Dall, of the N. W. 

 American coast, and can be distinguished from its nearest relative 

 by the bare anterior portion. The artist, deceived by the brilliant 

 surface, has carried the oblique grooves too far forward in the figure. 



YOLDIA PERPROTRACTA Dall 



Plate 18, fig. 3 



Yoldia perprotracta Dall, Smithsonian Misc. Coll.. vol. .59, p. 1, 1912. 

 Later Tertiary of the Canal Zone, Panama. U. S. Nat. Mus. Cat. No. 214350. 



