184 BULLETIN: MUSEUM OF COMPAEATIVE ZOOLOGY. 



and the distance to the base of the horn 0.35 of the transdiameter. The 

 apical pore is inclined a little to the right. 



The ventral area is not strongly defined and the pit is not far removed 

 from the girdle. 



The hypotheca is very rotund, its greatest diameter being slightly below the 

 girdle. Its total altitude is 0.8 of its transdiameter at the girdle, and its axial 

 altitude 0.6. The left antapical is longer than the right and is formed by a 

 blunt protuberant lobe whose width is half its height, bearing on its broadly 

 rounded antapex a one or two-ribbed fin strongly deflected to the right. The 

 right antapical is nothing but a finned spinule arising from the body, also 

 deflected to the right. 



The girdle is not oblique save in the distal third, where it is so deflected pos- 

 teriorly that its displacement is twice its width. The anterior ridge is heavy, 

 the posterior obsolete. The furrow is not impressed and is faintly ribbed. 



The plates are normal, the left intercalary large, subtriangular. The suture 

 lines are faint, marked by structureless bands. The plates are porulate with 

 or without faint reticulations of relatively large size. 



Length, 50 fj. ; transdiameter, 37 /x. 



Station, 4734. 



Heterodinium praetextum, sp. nov. 



Plate 7, Fig. 41. 



A very large species of the subgenus Euheterodinium with slender, tapering, 

 apical horn developed to a degree unusual in the genus. 



The body is elongated, its length 1.3 times the transdiameter and 1.7 times 

 the dorso- ventral. Epitheca exceeds the hypotheca in ventral view, and equals 

 it dorsally. Its altitude is 0.8 of its transdiameter at '.lie base, its ventral face 

 is excavated, its laterals convex in the median region and concave distally, and 

 the dorsal nearly straight. The apical horn is deflected to the right, and its 

 length is 0.25 of the altitude. The midventral suture is strongly deflected to 

 the left basally, and the ventral area is elongated, oblique, with eccentric pit. 



The hypotheca is broadly excavated ventrally, abruptly contracted dorsally, 

 and with feeble double curves laterally. The postindentation is shallow, form- 

 ing an asymmetrical arc, its depth 0.3 of the altitude of the hypotheca. The 

 antapicals are short, stout, bluntish. 



The girdle is slightly oblique and postmedian, forming a descending right 

 spiral displaced distally its own width. The furrow is scarcely impressed, 

 with deflected posterior list obsolete distally and decurrent on left antapex. 



The lonofitudinal furrow is short with low lists. 



The thecal plates are normal, and the walls reticulate with subequal, sub- 

 regular polygons which become smaller distally on the horns. The suture 

 lines are marked by broad bands with imperfectly developed areas of minute 

 reticulations. 



Length, 240 fi ; transdiameter, 180 /x. 



Station, 4740. 



