312 University of California Publications. [Zoology 



the diameter of the base and somewhat recessed and concave on 

 ventral face. Hypotheca of similar proportions but slightly 

 larger, with straight or slightly convex sides, also concave on the 

 right ventral face. Transverse furrow wide, about one-tenth of 

 the length in width, forming a descending right spiral with a 

 displacement of 1.2 times its width, deeply excavated, with low 

 heavy lists. Longitudinal furrow small, short and shallow, to the 

 left of the concave ventral face. Plates of the generic pattern, 

 antapicals very short, apicals long, sutures marked by rugose 

 ridges along the middle of the faint intercalary striae. Shell 

 with secondary longitudinal striae and intervening reticulations 

 forming irregular polygons. Transverse furrow traversed by the 

 longitudinal sutures and striae. 



Plasma dense, translucent (in fixed material), nucleus mid- 

 ventral, reniform, chromatophores large, ellipsoidal, yellowish 

 with brown center. About 15-20 disc-shaped and ellipsoidal per- 

 forate skeletal ( ?) inclusions in plasma mainly in the epitheca, 

 the single ones resembling the elements in the epithecal skeleton 

 of AmpJiilothiis elegans as figured by Schiitt ('95, Taf. 27, Fig. 

 102) but without their arrangement in a definite pattern. I have 

 seen similar inclusions but larger and less regular in the endo- 

 plasm of a large liolotrichous ciliate of the plankton in which this 

 species is found but am unable to determine from the scanty data 

 at hand, whether they are indigenous or adventitious with food 

 in the ciliate. Indeed this latter possibility is not entirely ex- 

 cluded in the case of Amphidoma, for as Schilling ('91) has 

 shown, there is a possibility that holozoic nutrition may occur in 

 some Dinoflagellata. These structures do not resemble any known 

 Coc eolith oplwriclae and I know of no organisms in the plankton 

 having normally such skeletal structures. 



This species differs from A. niicida Stein, the only other well 

 established species in the genus in its reversed proportions of 

 epitheca and hypotheca, wider girdle, longer apical and shorter 

 antapical plates, in its rugose suture lines, surface structure and 

 skeletal (?) inclusions. 



Dimensions : length, 71/x ; diameter at girdle lists, 41/x. 



Taken in vertical haul from 70 fathoms, 7 miles off Pt. Loma 

 in July. 



