504 MEMOIKS OF THE UNIVERSITY OF CALIFORNIA 



The ocellus is relatively very large, its length is 0.55 transdiameter and its main axis inclines 

 45° to the right and ventrally from the major axis of the body. It protrudes considerably 

 beyond the contour of the body, especially in ventral view, and crowds the intercingular sulcus 

 anteriorh' and the anterior flagellar pore almost to the anterior margin. The lens somewhat 

 exceeds a hemisphere, its diameter is 0.35 transdiameter. It is composed of concentric laminae 

 with a brilliant iridescence of spectral colors. The pigment mass is also regularly hemispherical 

 without lobes or detached granules and receives the base of the lens in its flattened side. The 

 black melanosome encloses a rather large coral-red core which shines through the thin layer of 

 black pigment. 



The nucleus is a very elongated ellipsoid placed transversely across the equatorial region. 

 Its major and minor axes are 0.75 and 0.33 transdiameter respectively in length. It is possible 

 that it is in transformation prior to mitosis. No chromatin net and perinuclear zone were noted. 

 Pouch-shaped pusides with pinkish contents arise from the two flagellar pores. They are of 

 equal size and 0.25 transdiameter in length. No food balls or vacuoles or chromatophores were 

 found. Several greenish globules lie near the sulcus on the ventral face and a number of minute 

 greenish vacuoles were scattered in the peripheral plasma. The general color was a pearl grey. 



BmExsioxs. — Length, 48/^; transdiameter, 35/^; length of nucleus, 26/^; length 

 of extended (?) tentacle, 26/^; length of ocellus, 19/^. 



OccT^RRENCE. — T^Y0 individuals seen. These were taken Avith a No. 25 silk 

 net in the Pacific Ocean off La Jolla on July 20 and August 13, 1917, respec- 

 tively. The hauls were made from depths of 80 and 83 meters to the surface and 

 in surface temperatures of 20-6 C and 21-7 C resiDectively. 



Activities. — The individuals seen were not as active as those of E. extrudeiis 

 or E. pnvillardi, and the tentacle was subject to only feeble contractions as 

 observed by us, although there was no evidence that this inactivity was due to 

 the ajiproach of cvtolysis. 



Comparisons. — This is the smallest species of the genus. It is possilile that 

 it is a juvenile stage of some other form, although the morphological evidence 

 for structural transformations with growth as the individual grows older are 

 slight among dinofiagellates. It is nearest to E. cornuta (Sehiitt) in structure, 

 but is not only smaller, 48/^ as compared to 104/^, but has a different type of 

 prod, tentacidar recess, shape of body and nucleus, and lacks the apical hoi*n. 



The position of the longitudinal fiagellum at the right side of the tentacular 

 recess and hehind the prod is confirmed by the jDresence of the posterior pore 

 and pusule. In Sehiitt 's figure (1905, pi. 26, fig. 96) of E. cornuta the posterior 

 fiagellum is represented as arising at the base of and ventral to a spherical 

 structure which we interpret as the capitate end of the prod. The fiagellum 

 figured by Sehiitt is remarkably stout and peculiarly wavy. It is possible that 

 its origin is correctly figured ; if so, the location of the posterior flagellar pore 

 differs remarkably in different species of Erijthropsis. It is also possible that 

 its origin is dorsal to this tentacular knob, not ventral as figured. If so, this 

 location is homologous to that in E. viinor. It is possible that the extreme 

 thickness of fiagellum figured by Sehiitt is due to contraction and may not 

 represent a frayed-out, axial tentacular fiber exposed by partial cytolysis, as its 

 structure figured by Sehiitt might suggest. The imdoubted presence of the 



