52 THE NAUTILUS. 



irregular; anterior slope with strong radial striae originating 

 below the septate growth and extending to the anterior margin, 

 similar striae appear on the left lateral slope, but are scarcely, 

 if at all, visible on the right slope; the septate portion of the 

 shell is small in comparison with the adult expansion, it is nar- 

 row and the posterior portion covered by the septum is free 

 from and projects over, but scarcely beyond, the posterior mar- 

 gin of the adult aperture; the first growth of the shell from the 

 septate form is continued on the sides in a nearly direct con- 

 tinuation of the lateral slopes of the septate shell for some 

 little distance, the anterior slope of this stage is also a continu- 

 ation of the anterior slope of the septate stage but owing to the 

 oblique position assumed by the septate shell is at first some- 

 what convex, as viewed laterally, later as the side slopes begin to 

 expand, the anterior slope is continued in a nearly straight line to 

 the margin; the left lateral slope of the adult shell below the sec- 

 ondary constriction is concave at first, becoming nearly straight 

 toward the margin; the right lateral slope is less concave above 

 and straighter and more oblique than the left; owing to the 

 small size of the septum and consequent large aperture of the 

 septate shell and the narrow first growth of the adult shell there 

 is no distinct aperture to the septate portion visible in the 

 adult shell from below, the whole interior of the adult shell 

 appears to pass, practically unconstricted, directly into the 

 septate portion; the posterior margin of the adult shell narrow 

 and somewhat abruptly expanded and reflected. 

 Length 5.5; width 3.75; alt. 1.75 mm. 



The septate shell is oblong, the sides being nearly parallel, 

 but slightly expanding anteriorly, the right slightly convex and 

 the left slightly concave; the posterior margin is regularly 

 rounded; the anterior more broadly rounded; the apex de- 

 pressed, bluntly rounded, excentric, reaching nearly to the 

 right margin, smooth except for slight concentric wrinkles, lines 

 of growth fine and regular; the anterior slope is slightly convex; 

 the very short posterior slope below the projecting apex to the 

 line of the septum is straight and oblique; the right lateral 

 slope is steep and nearly straight, the left slope very convex; 

 the septum is very short, being less than half of the length of 



