180 bulletin: museum of comparative zoology. 



dorso-ventral extension. Epitheca scoop-shaped, excavated ventrally, flaring at 

 the girdle. Its altitude 0.75 of a transdiameter. Apex with broadly sloping 

 slightly convex margins, which turn abruptly posteriorly to a broad, deep con- 

 striction just below the level of the ventral area, below which it abruptly ex- 

 pands to the girdle, thus giving to the epitheca a form which suggests the body 

 of a violin. The ventral area is ellipsoidal, with the pit at its anterior end. 



The hypotheca is somewhat shorter than the epitheca, its ventral altitude 

 being less than 0.75 of a transdiameter. It is constricted somewhat rapidly, 

 reaching 0.5 of a transdiameter at the level of the base of the antapicals. The 

 antapicals are short, stout, acute, and divergent, their tips being less than 0.5 of 

 a transdiameter apart. The postindentation is less than 0.25 of a transdiameter 

 in depth and is broadly rounded. 



The girdle is but slightly oblique, is displaced its own width, and is obsolete 

 distally, its posterior ridge being decurrent on the right antapical. The furrow 

 is deeply impressed, has very prominent ridges and coarse reticulations. 



The thecal plates are normal. The left intercalary plate of the epitheca is 

 unusually large. The reticulations are porulate, relatively large, and somewhat 

 irregular. 



Length, 123 /u; transdiameter, 83 /x. 



Station, 4228. 



Heterodinium gesticulatum, sp. nov. 



Plate 6, Figs. 37, 38, 39, 40. 



A medium-sized species with rounded apex, right antapical deflected strongly 

 to the right and the posterior angle of the postcingular plates on the left margin 

 of the hypotheca strongly protuberant. 



Body moderately elongated, the length 1.6 to 2.3 times the transdiameter 

 (measured on the anterior ridge of the girdle). The epitheca is shorter and 

 distinctly wider than the hypotheca. Its apex is broadly rounded, almost 

 semicircular in face view, but the ventral face is not deeply excavated or scoop- 

 shaped. It is often wider anteriorly than it is at the girdle, and may have a 

 slight constriction just anterior to the girdle. The ventral area is irregularly 

 squarish with central pit. 



The hypotheca is narrower than the epitheca, its transdiameter at the girdle 

 being 0.9 to 0.75 of that of the epitheca. Its ventral surface is flattened, the 

 dorsal one rotund. The posterior part of the hypotheca beyond the suture be- 

 tween the postcingular 1 and antapical plates is deflected to the right, in ex- 

 treme cases as much as 40°. The right antapical is deflected more than the 

 left, attaining even 45° to the main axis, while the left is only 5°-10° or sub- 

 parallel to the axis. The right margin of the epitheca is deeply concave, while 

 the left is carried out in a more or less prominent, often decurved angle at the 

 point just anterior to the suture between the left postcingular and the left ant- 



1 These plates were called postmedians in my earlier paper (: 05), On Hetero- 

 dinium, etc., Univ. of Calif. Pubs. Zool., 2, p. 345. 



