Bartsch — A New Classification of the Shipwor7ns. 27 



is crossed by strong lines of growth, which extend over the posterior median 

 part. The anterior part forms a strong auricle, which is conspicuously 

 separated from the posterior median portion, the shell here bending strongly 

 inward. The auricle is marked by more or less curved lines of growth, 

 which give one the false impression of raised cords. The interior of the 

 shell is bluish white. The umbone projects inward as a strong knob, and 

 the blade springs from deep within the umbones, and makes a decided curve, 

 the early portion having the broad side of the blade parallel to the inner 

 surface of the shell, that is within the umbones, while within the median 

 portion of the shell the blade becomes twisted, so that it assumes an oblique 

 position to the inner surface of the shell. The suture of the anterior and 

 the median portion is marked by a slightly tumid area. The middle median 

 portion is decidedly roughened and bears the usual knob at the ventral, 

 margin. The auricle extends over the median portion on the inside as a 

 strong shelf. The inside of the auricle shows the same translucent cordlike 

 lines apparent on the exterior. The pallettes are of the cone-in-cone shape 

 variety, the individual cones being semicircular in cross section, the inner 

 free border being straight, while the outer is curved. The cone elements 

 are rather distantly spaced. The free margin of the membrane of these 

 cone-in-cone elements is finely denticulated. 



The type, Cat. No. 341,128, U. S. N. M., was taken from greenheart tim- 

 ber of the canal locks at Balboa, Canal Zone, by Mr. James Zetek, and meas- 

 ures: length, 10.2 mm.; altitude, 9.5 mm. The paUettes 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 pallettes, 

 3.4 mm. 



Bankia (Bankiella) mexicana, new species. 

 Shell subglobular. Anterior portion, excepting the extreme smooth cal- 

 loused area, brown; the rest of the shell white. The extreme anterior por- 

 tion 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 toward 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 portion. The den- 

 tal ridges on this part are closely crowded and separated 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 slightly 

 concaved area extending from the umbone to the ventral margin, and this 

 part is crossed by curved rough wrinkles which evanesce on the posterior 

 median portion. The median groove bears a strongly rounded knob at the 

 ventral margin. The posterior portion forms a strong auricle which is sepa- 

 rated from the median by a sudden depression in the curve of the shell. The 

 interior of the shell is bluish white. A strong knob marks the umbones, 



