KOFOin AND SWEZY: UNARMORED DINOFLAGELLATA 



15 



and well defiuecl, with clearly marked, equal borders. Its length A'aries from 

 0.5 of a turn around the body in Hemidiniiim (fig. C, 1) to four complete turns 

 in the more highly specialized species of Cochlodinium (fig. C, 10). It may 

 form a complete circle about the bod}^ as in a few of the simpler Gijmnodinium 

 (figs. X, 1, 2, 8), or its ends may become displaced, so that the distal end conies 

 to lie nearer the posterior region of the body than to the proximal end, as in 

 Gyrodiniiim (fig. CC). Its course thus becomes a more or less steep, spiral 

 path around the body. 



Fig. C. Types of girdle arrangement. 1. Hcmidinium nasutum Stein. After Stein (1883, pi. 2, fig. 24). 

 2. Amphidinium steini (Stein). After Stein (1883, pi. 17, fig. 9), slightly modified. 3. Amphidinmm scissum 

 sp. nov. 4. Gymnodinium doma sp. nov. 5. Gymnodiiiium rubrum sp. nov. 6. Gyrodinium spumantia sp. nov. 

 7. Gyrodinium contortum (Schiitt). After Schiitt (1895, pi. 21, fig. 65). 8. Cochlodinium pirum (Schiitt). After 

 Sehiitt (1895, pi. 23, fig. 76). 9. Cochlodinium clarissimum sp. nov. 10. Cochlodinium augxistum sp. nov. X 500. 



AVitli this posterior displacement of the distal end of the girdle an increase 

 in length takes place which, in some of the species in Gyrodinium, becomes 

 greater than one turn of the body (figs. CC, 22; DD, 17). This produces a 

 torsion of the body which continues with the increasing length of the girdle 

 until it may make two (fig. C, 9), three (fig. HH, 16), or even four com])lete 

 turns of the body, which is the inaxuuum length reached in Codilodiiiium 

 (fig. C, 10). Closely correlated with the length of the girdle and the resulting 



