10 BULLETIN 122, UNITED STATES NATIONAL MUSEUM. 



distantly spaced. The free margin of the membrane of these cone- 

 in-eone elements is finely denticulated. 



The type, Cat. No. 341128, U.S.N.M., was taken from greenheart 

 timber of the canal locks at Balboa, Canal Zone, by Mr. James Zetek, 

 and measures: Length, 10.2 mm.; height', 9.5 mm. The pallets 

 measure: Length. 12 mm., but they are probably longer because the 

 basal stalk seems slightly broken ; 8 mm. of this length go to the blade. 

 Diameter of pallets, 3.4 mm. 



Subgenus Bankiella Bartsch. 



1921. Bankiella Bartsch, Proc. Biol. Soc. Washington, vol. 34, p. 26. 



Pallets consisting of a series of cone-in-cone elements covered by 

 a thin membrane which is neither fimbriated nor denticulated at the 

 free margin, but entire. 



Type. — Bankia {BanMeJla) mexicana Bartsch. 



KEY TO THE AMERICAN SPECIES OF BANKIELLA. 



Pallets : 



Outer distal edge of segments strongly concavely curved gouldi 



Outer distal edge of segments slightly concavely curved mexicana. 



Shell : 



Middle portion of median part narrow gouldi 



Middle portion of median part very broad mexicana. 



BANKIA (BANKIELLA) MEXICANA Bartsch. 

 MEXICO SHIPWOBM. 



Plate 8, fig. 1; plate 30, fig. 2. 



1921'. Bankia (Bankiella) mexicana Baktsch, Proc. Biol. Soc. Washington, 

 vol. 34, pp. 27, 28. 



Shell subglobular. Anterior portion, excepting the extreme smooth 

 calloused area, brown; the rest of the shell white. The extreme an- 

 terior portion forms a sinus from which a thin callus is reflected over 

 the anterior dental ridge-bearing portion. The dental ridges radiate 

 from this anterior smooth area backward, spreading out more or 

 less fan shaped, the spaces between the ridges becoming wider to- 

 ward their distal end, where they are about twice as wide as the 

 dental ridges. These dental ridges are rather coarsely denticulated 

 at their free margin. Fifty-one of these ridges can be counted, 

 though it is possible that some of the earlier ones have been lost 

 through the erosion of the umbones. The denticles on these dental 

 ridges are not nearly as strong as those on the anterior median por- 

 tion. The dental ridges on this part are closely crowded and sepa- 

 rated by mere impressed lines. They terminate posteriorly in a 

 straight line that extends from the umbones to the ventral margin. 

 The middle median portion is a slighly concaved area extending 

 from the umbone to the ventral margin, and this part is crossed by 



