MONOGRAPH OF AMERICAN^ SHIPWORMS, 11 



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 separated 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, from the inside of which the slender blade 

 curves downward into the cavity of the shell. This blade has its 

 broad side obliquely placed to the inner curvature of the shell. The 

 anterior portion is separated from the median by a thickened cord, 

 and a roughened area marks the middle median portion of the shell. 

 The postarior area projects over the posterior median portion as a 

 shelf. The pallets are of the cone-in-cone type, the distal margin 

 of the cones being entire. 



The type, Cat. No. 194l76fl, and a lot of additional specimens were 

 collected by Mr, C. R. Orcutt on dead mangroves at Sinaloa, Mexico. 

 The type measures: Length, T mm.; height, 6.5 mm. The pallets 

 are all fragmentary, and hence it is impossible to give their measure- 

 ment. 



BANKIA (BANKIELLA) GOULDI Bartsch. 

 GOULD SHIPWORM. 



Plates 2, 3, and 8, fig. 3 ; plates 9-16 ; plate 30, fig. 4. 



1908. Xylotnja youldi Bartsch, Proc. Biol. Soc. Washington, vol. 21, pp. 211, 



212 



Sliell subglobular, milk-white. The extreme anterior part with an 

 incised sinus which is covered with a smooth callus that is reflected 

 over part of the anterior portion, terminating in a rather thickened 

 ridge. The anterior portion is marked by a series of dental ridges 

 which are separated by spaces about one and a half times as wide 

 as the dental ridges. These ridges slope slightly more abruptly on 

 the umbonal side than on the ventral side, and are finely denticulated 

 at their free margin. There are 52 in the type. The junction of the 

 anterior part with the anterior median portion forms a strong im- 

 pressed line, which extends from the ventral margin to the umbones. 

 The anterior median portion is marked by a series of dental ridges 

 which meet those of the anterior part at almost right angles. These 

 are provided with strong denticles. The center of the middle por- 

 tion of the median part bears a strongly impressed groove, which 

 extends from the ventral margin to the umbones. The entire median 

 portion is covered with enfeebled nondenticulated upturned ex- 

 tensions of the dental ridges of the anterior median portion, which 

 lends this part of the shell a rather rough appearance. The posterior 

 median portion is about as wide as the anterior and median parts, 

 and is marked by obliquely curved lines of growth. The posterior 

 part forms a strong auricle, well constricted at the junction with the 



