KOFOID AND SWEZY: UNARMORED DINOPLAGELLATA 363 



The sulcus occupies the trough between the two high ridges formed by tlie spiral course of 

 the girdle. It follows a descending spiral course which makes about one turn of the body. The 

 last part of its course is longitudinally directed, terminating at the antapex. The flagellar pores 

 are not figured. 



The nucleus is spheroidal and is posterocentrally located. Its axis is about 0.3 transdiametcr 

 in length. 



The cytoplasm is apparently granular with a few small spherules anterior to the nucleus and 

 is diffusely colored rose pink. 



Dimensions.— Length, 90/^ ; transdiametcr, 65m ; diameter of nucleus, 21m. 



Occurrence. — Figured by Selilitt (1895) from the material of the Plankton 

 Expedition, presimiably from the Bay of Naples or the Atlantic. 



Co:\rPARisoNS. — C. con fit rid urn is one of the few I'ed or rose colored species 

 of the genus, sharing this feature with C. archimedes (Pouchet) Lemm., C. 

 rosaccum sp. nov., and C. mdiafuvi. It is unlike anv other species in the salient 

 ridge in which the girdle lies, this usually l)eing a region of constriction. 



Cochlodinium convolutum sp. nov. 



Plate 10, figure 115; text figure HH, 5 



Diagnosis. — A rather small species with subovoidal ])ody, contracted anter- 

 iorly, its length 1.4-1 transdiameters ; girdle a descending left spiral of 1.6 turns, 

 displaced 0.82 transdiameter ; sulcus with apical and antapical loops and torsion 

 of 0.8 turn; color, green. Length, 49m. Pacific off La Jolla, California, July, 

 August. 



Description. — The body is subovoidal with broad apices, widest posteriorly, nearly circular 

 in cross-section, its length 1.44 transdiameters at the widest part. The anterior end is rounded, 

 the posterior end deeply excavated by the suleal notch. The epicene is exceeded in size by the 

 hypocone, its length being greater but its transdiameter less. It is convex-conical with a slight 

 concavity on the dextrodorsal side in the region of tlie anterior junction of the sulcus and girdle. 

 It has a length from the proximal and distal ends of the girdle of 0.27 and 0.81 respectively of 

 the total length of the body. Its posterior portion is a slender pointed band which makes about 

 0.6 turn around the body. The hypocone is less symmetrical than the epicone, its ventral face 

 abutting on the girdle and sulcus, usually drawn out in a baglike extension which is separated 

 posteriorly from the dorsal surface by the suleal notch. 



The girdle is a descending left sjjiral of 1.6 turns and a displacement of 0.82 transdiameter, 

 its proximal and distal ends having a distance from the apex of 0.27 and 0.81 respectively of 

 the total length of the body. The first 0.6 transdiameter of its coui'se is nearly transverse, 

 turning posteriorly with an angle of about 30° with the transverse plane on the sinisti'odorsal 

 surface, flattening to a nearly transverse j)lane in the dextrotlorsal surface and again turning 

 posteriorly in the last part of its course on the ventral face. The furrow has a width of about 

 0.05 ti'ansdiameter and is usually deeply impressed with rounded, overhanging borders. 



The sulcus invades the epicone in a short wide loop which tei-minates below the ape.x on llie 

 right side, or it may partly encircle the apex. IJeyond the anterior flagellar i)orc' it turns to the 

 left in a descending spiral course with a torsion of 0.8 turn. The furrow is narrow, less than 

 half tlie width of the girdle, widening slightly posteriorly where it deeply notches the antapex. 

 The anterior flagellar port' is located at the anterior junction of the girdle and sulcus, the 

 posterior pore slightly beyond the posterior junction. 



