KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 203 



the surface it resembles G. costatum. It belongs in the subgenus Lineadinium, 

 in which no other species approximates it in size, proportions, or nature of the 

 surface, except G. costatum, as above noted. 



Gymnodinium diploconus Schiitt 



Text figure Y, 6 



Gyninodimnm diplocoiius Sehiitt (1895), ])1. 24, fig. 78. 

 G. diploconus, Sehiitt (1896), p. 5, fig. 5, B, C. 

 G. diploccnus, Lemmermann (1899), p. 358; (1910), p. 618. 

 G. diploconus Entz, Jr. (1902), p. 92; (1905), p. 108. 



Diagnosis. — A medium sized species, with biconical body with subtruncate 

 apices, its length 1.24 transdiameters ; girdle Avithout displacement; sulcus ex- 

 tending from the girdle to the antapex; surface finely striate. Length, 57/^. 

 Atlantic or Bay of Naples ; Pacific off La Jolla, California, June, July. 



Description. — The body is biconical, broadly flaring in the middle region around the girdle 

 and tapering to the broadly su1)truneate a ibices, its length 1.24 transdiameters at its widest part. 

 It is nearly circular in cross-section. The hypocone and the epicone are subeqnal. The epicone 

 is conical, about 55° in the anterior part, the postei'ior portion flaring at the girdle. It has a 

 length of about 0.39 to 0.50 of the total length of the body. The conical portion of the hypocone is 

 slightly narrower than the epicone (40°) with the anterior i)ortion flaring broadly to meet the 

 girdle. The antapex is blunt with a small sulcal notch. Our specimen (fig. Y, 6) is broader 

 and stouter than that of Sehiitt (1895). 



The girdle is premedian in position, having a distance of about 0.39 of the total length of 

 the body from the apex or may be median and equatorial. It follows a circular path around 

 the body with no posterior displacement or with a displacement of less than half its own width. 

 The furrow is narrow and deeply imbedded with overhanging borders. The sulcus extends 

 from the girdle to the antapex, following a slightly sinuous course. The anterior flagellar pore 

 is located at the anterior junction of the girdle and sulcus, the posterior pore is about midway 

 between the girdle and antapex. 



The nucleus is a spherical body centrally located. Its diameter is about 0.24 transdiameter 

 of the body in length. Numerous spherules of varying size are found in the hypocone, especially 

 numerous at the antapex, and fewer in the epicone. Stout, rod-shaped, yellowish chromatophores 

 are scattered through the peripheral zone. The surface is covered with fine longitudinal striae, 

 about equal in number on both ends of the body, and about 30 across the ventral face. 



Dimensions.^ — Length, 57-80/^; transdiameter, 46-6?,/' ; diameter of nucleus, 

 12-20/^. 



Occurrence. — This was figured by Sehiitt (1895) from the collections of 

 the Plankton Expedition from the Bay of Naples or from the Atlantic. It 

 also occurred at La Jolla, California, in collections made June 30, 1904, in a 

 liaul 12 miles offshore, from 300 meters to the surface, and on July 5, 1904, 10 

 miles offshore, in a haid from 290 meters to the surface. 



Co:\rPARTS()xs. — This belongs in the subgenus Li)iea(li)iiinii, and stands near 

 G. hdcrodriatam nom. sp. uov. (fig. Y, 7), but has equal numbers of striae on 

 both ends of the body. In the iuuiil)er and fineness of its striae it resembles G. 

 radiatum sp. uov. (fig. Z, 9) and (/. niiiUilineatum sp. nov. (fig. Y, 18). 



