KOFOID AND SWEZY: UNARMORED DINOPLAGELLATA 417 



The girdle forms a steep, maiform, descending left spiral of about 30° from the horizontal. 

 It passes from its anterior junction with the sulcus 0.09 total length from the apex to its distal 

 junction 0.67 total length with little change in obliquity. Its total displacement is 0.58 total 

 length or nearly 1 transdianu'ter. The furrow is about 0.08 transdiameter in width and is 

 lightly impressed without prominent lips. The sulcus runs from near tlie ajjcx almost to the 

 antapex, with only a slight sigmoid curve. The anterior flagellar pore is at the anterior junction 

 of girdle and .sulcus and the posterior a girdle's width below the posterior junction. The 

 transverse flagellum is less than 0.5 the length of the gii-dle and the posterior one 1.25 lengths 

 of the body in length. 



The ocellus is 0.28 transdiameter in length and at the right of the center of the body. It is 

 diffusely organized. The lens is a broadly ovoidal, translucent body 0.22 transdiameter in length 

 and 0.9 of its length in width, and truncated at the end applied to the melanosome. There are 

 no laminae visible. The melanosome consists of a dense cluster of coarse black or very dark 

 brownish black granules clustered in a small hemisphere 0.5 diameter of the lens in diameter 

 applied to the center of the truncated anterior end of the lens. 



• The nucleus is a small ellipsoidal body lying obliquely in the posterodextral part of the 

 body. Its major and minor axes ai'e 0.40 and 0.26 transdiameter in length respectively. It is 

 filled with coarse, beaded, chromatin strands running spirally about the major axis. No pusules 

 were noted. The body was crowded with food and tlie products of metabolism. Near the center 

 was a very large, ellipsoidal, fluid-filled vacuole of a very pale, ochraceous-salmon color. Crowded 

 about it were numerous highly refractive bluish green spherules of varying sizes ; while crowded 

 into the posterosinistral corner was an ellipsoidal food ball of yellow ochre color with a brownish 

 mass within it. Faint ti'aces of longitudinal .sti'iae could be detected on the surface. 



Dimensions. — Length, al)oiit 50m; transdiameter, 34/*. 



OcCTJEEENCE. — One individual observed in the plankton of the Bay of Naj)les 

 on January 27, 1908, by the senior author. 



Activities. — The animal circled in close clockwise sj^irals several lengths 

 of the body in diameter. The transverse flagellum was seen to be thrown out 

 of the girdle aud trailing behind the body, near the longitudinal one, as a spiral 

 band at times while the animal was moving. As eytolysis approached the distal 

 end of the longitudinal flagellum formed an amoeboid mass of plasma vrhich 

 retreated towards its base. This organism was photosensitiA-e to the illumi- 

 nation of the microscope, contracting into a more I'oiuided-up form when 

 intensely illuminated and extending again into the pointed form of apex in 

 dimmer light. 



CoMP.AEisoxs. — This species has the GijrodiuiiiDi type of girdle and sulcus 

 while P. nigra (fig. LL, 1) has the Gtjmnodiuium type and P. ochrea (fig. LL, 4) 

 stands aliout midway between the two in this feature. This species is placed 

 in Profopsis rather than PoKclictid iK'cnuse of the absence of torsion in the 

 sulcus. The ocellus also shows an adA'ance in that the lens is a unit instead of 

 several as in P. nigra. It is, however, less hyaline than usual in such structures. 

 The melanosome is unique in being conqjosed of a loose aggregate of uniform, 

 small, dark brownish black grains grouped in a small liemispliere on the trun- 

 cate end of the lens. It is relatively unusually small, having only 0.5 the diam- 

 eter of the lens and less than 0.1 its volume. The lack of integration in this 

 organ is also seen in tlie fact that it does not, at least in the single individual 

 observed, ha^■e the customary position neai- the periphery at the left of the 



