KOFOID AND MICHENER: DINOFLAGELLATES. 275 



Amphidoma spinosa (Kofoid). 

 Murrayella spinosa Kofoid (1907) belongs in this genus. 



Amphidoma elongata, sp. nov. 



Resembling A. acuminata Stein in form but more obtuse anteriorly and with 

 its bluntish antapical horn curved a little ventrally. Body elongated, bi- 

 conical, its length 2 transdiameters. Epitheca and hypotheca equal in alti- 

 tude, both with concave sides, except near girdle end on right face of hypotheca 

 which is fuller. Apex somewhat abruptly rounded to small apical closing 

 platelet. Antapex blunt, curved ventrally beyond basal constriction, with- 

 out acicular spinule of A. acuminata. Girdle scarcely displaced, slightly im- 

 pressed. Ventral area very slightly indenting epitheca, widening to the right 

 to 0.7 girdle width just beyond the girdle and attenuate posteriorly, its total 

 length only 3 girdle widths, guarded by two minute lists. Plate formula 

 6', 0°, 6", 6, 6'", 1p, 1"". Apical V an elongate, asymmetrical rhomb, other 

 apicals 0.66 transdiameter in length; precingular 6" pentagonal; postcingular 

 V" small, triangular; posterior accessory large, 2 girdle widths across; 

 antapical 1"" asymmetrical. Surface smooth, ventral pore on right edge of 

 apical 1'. Faintly striate intercalary band along apical-precingular suture. 



Length 35 to 45 m; transdiameter, 18 to 23 fi. 



Sta. 4720. 



Amphidoma laticincta, sp. nov. 



A minute spheroidal species with smooth surface. Body almost a perfect 

 sphere, its length not exceeding 1.05 transdiameters. Epitheca and hypo- 

 theca equal, hemispherical, the apex slightly contracted and a slight depres- 

 sion sometimes seen at apical-precingular suture. Girdle not displaced, 

 relatively wide, scarcely impressed, without lists. Ventral area not indenting 

 the epitheca, less than a girdle width across at posterior margin of girdle, 

 attenuate, and extending posteriorly less than two girdle widths, with two 

 small lists overhanging flagellar pore. Plate formula 6', 0", 6", 6, 6'", l p , 1"". 

 Apical 1' narrower than other apicals, asymmetrically diamond-shaped, not 

 parting precingulars 1" and 6" to meet the ventral area. Precingulars a 

 trifle shorter than apicals. Postcingular V" very minute, nearly rectangular, 

 posterior intercalary elongated laterally, narrow. Surface smooth and 

 structureless except for faint surface lines and intercalary band at apical- 

 precingular suture. Ventral pore at midventral posterior tip of apical 1'. 



Length IS m,' transdiameter, 17 m- 



Sta. 4720. 



