KOFOID AND MICHENER: DINOFLAGELLATES. 299 



Length, greatest anteroposterior extent of midbody, 20 m, total 80 /x; 

 dorso-ventral extent of midbody, 41 /x, total, 42 p. 



Sta. 4724. 



HlSTIONEIS REGINELLA, Sp. nOV. 



Most resembles H. gubernans Schiitt, but differs from it in its relatively 

 larger, more rotund midbody, and greatly sacculated posterior collar. The 

 body is broadly and symmetrically rounded posteriorly in lateral view, with 

 flattened anterior margin, slightly elevated at base of inner collar. In dorsal 

 view the body is contracted anteriorly. The collars and fins are superficially 

 as represented by Schiitt (1895), pi. 5, fig. 23, with a number of differences in 

 details. The inner collar is not so wide distally, is coarsely reticulate within 

 the distal zone of radial ribs. The posterior collar is considerably larger, 

 sparingly ribbed distally, and bears on each side, well toward the ventral 

 face, a pendant sac-like expansion, over 0.75 of the dorso-ventral diameter 

 of the midbody in length. The apices of these sacs are reticulated. The 

 ventral and postero-ventral fins are similar to those of H. gubernans except 

 that both dorsal and ventral margins are curled to the right. Phaeosomes 

 ellipsoidal. 



Length, antero-posterior of midbody, 23 /x, total, 55 n) dorso-ventral 

 diameter of midbody, 19 ju, total, 33 /j.. Phaeosomes, 2.5 ix. 



Sta. 4681. 



HlSTIONEIS ROTUNDATA, sp. nOV. 



A minute species with midbody of H. remora Stein and collars and fins 

 resembling those of H. para Murr. and Whitt., but differing from the species 

 figured by Stein (1883), pi. 22, fig. 11, in more rotund midbody, shorter and 

 wider postero-ventral fin, shorter anterior collar, and longitudinally ribbed 

 posterior collar. From Murray and Whitting's (1899), pi. 32, fig. 4, species 

 it differs in the narrower neck of midbody, slenderer stalk of anterior collar, 

 and wider ventral fins. Body almost spheroidal, with mound-like elevation 

 at base of anterior collar. Anterior collar low, 0.5 dorso-ventral diameter 

 of midbody in height, its apical diameter about equal to that of midbody, 

 with a few short ribs. Posterior collar nearly vertical, 0.3 to 0.5 dorso-ventral 

 diameter in height, with 5 aciculate ribs on the side. Ventral fin 2 dorso- 

 ventral diameters from lip of posterior collar to antapical end, swelling ven- 

 t rally posterior to fission spines, tapering to blunt antapex, with stout bowed 

 posterior rib, 0.8 dorso-ventral diameter in length. Fin faintly reticulate 

 basally. Surface minutely areolate, with 11 pores on right face. 



Length, of midbody, 17 ju, total, 38 m5 dorso-ventral diameter, of midbody, 

 13 n, total, 16 fx] transdiameter, 13 /x. 



Sta. 4720. 



