388 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.42. 



does not show the low, angular elevations seen in the left valve. In 

 this right valve the umbonal angle with the posterior part of the 

 hinge is nearer 80° than 70°. 



Locality. — East side Seward Neck. 



Eolotype and faratyjpe. — Cat. No. 58437, U.S.N.M. 



EURYMYELLA ? SIMULANS, new species. 

 Plate 49, figs. 12, and 13. 



Shell small, modiolopsoid in form, with straight hinge line, beak 

 slightly arching over the hinge border, flattened, not prominent, sit- 

 uated about one-third distance back from front end of hinge. Pos- 

 terior margin nearly at right angles with the cardinal margin ; anterior 

 end narrow. Umbonal ridge broad, not sharply defined. Posterior 

 slope plano-convex to the posterior margin. In front of the umbonal 

 ridge there is a broad, shallow furrow, producing a slight reentrant 

 curve to the lower margin of the shell. This character, strictly 

 speaking, removes the species from the genus EurymyeUa, the entire 

 absence of a mesial sulcus having been adopted as one of the dis- 

 tinctive characters of the genus. It is, however, placed in the genus 

 because of the extremely close resemblance in aJl other particulars 

 to the abundant representatives of the genus with which it appears 

 associated. There is also the possibility that the appearance of the 

 sulcus, which is quite distinct, may be the residt of accident or 

 of abnormal growth. Close examination of the smaller specimen 

 shows a crack line in the bottom of the sulcus, and the larger speci- 

 men shows an angular projection of one of the growth-laminae in the 

 sulcus near the center of the shell. I am of opinion, therefore, that 

 the peculiarity is either a varietal modification of a representative 

 of the genus EurymyeUa or that this character is due to accident. 

 Surface covered by faint concentric lines and stronger occasional 

 lines of growth. 



Dimensions of the type-specimens are: (1) Length, 16 mm.; height, 

 11 mm. (2) Length, 23§ mm.; height, 18 mm. 

 - Locality. — East side of Seward Neck. 



Coty:pes.—€^i. No. 58438, U.S.N.M. 



EURYMYELLA PLANA, new species. 

 Plate 49, fig. 14. 



Shell ovoid in outline, beak greatly depressed, surface gently con- 

 vex, with greatest convexity in center of the shell. Both cardinal 

 angles rounded, giving to the outline a subregular ovoid form. 

 Surface markings fuie, concentric lines, and occasional longer irreg- 

 ular gi'owth lines. 



Dimensions. — Greatest diameter from the antero-cardinal angle to 

 the postero-ventral margin 25 mm.; greatest diameter at right 



