179 



four apicals. In the case of C. hirundinella and C. candelabrum he finds 

 four plates in each of the series which he designates as pre-and post- 

 equatorials. He finds but one antapical phite, and adds much to our 

 knowledge of the obscure details of the ventral plate, longitudinal furrow 

 and attachment region. 



I shall use the term apical for the anterior series of plates only, 

 and shall designate the series anterior to and contiguous to the girdle 

 as precingular (prec), and that posterior to and contiguous to it as 

 postcingular (poste), and the posterior ones as antapicals (antap.). 

 These names are distinctive of the four series and are widely applicable 

 throughout the Dinoflagellates. 



The theca of Ceratium is composed of four series of plates, two 



poste. 



aniop. 



Fig. 1. Ventral view of Ceratium fitrca. X 350. In this and the following- figures 

 the apical plates are numbered 1' — 4', the precingulars 1" — 5", the postcingulars 

 1'" — 4"', the antapicals 1"" and 2"", and the girdle plates (numbered only in Fig. 1 



and 2) 1—4. 



Fig. 2. • Dorsal view of G. furca. X 350. 



Fig. 3. Ventral view of G. ftcstts, region of the midbody only. X 530. ap, ajiical 



series; j)rec, precingular series; poste, postcingular series; antap, antapical series of 



plates; v.p, ventral plate. 

 Fig. 4. Dorsal view of C. fastis. X 530. 



in the epitheca anterior to the girdle, and two posterior to it in the 

 hypotheca, with a series of four narrow trough-like girdle plates be- 

 tween. There is in addition to these the so-called ventral plate (v. p.) 

 which is a thin membranous sheet scarcely comparable with the rest of the 

 thecal wall in structure and not belonging to any of the series, but inter- 

 calated on the ventral face in the midventral line extending through 

 both the pre- and postcingular series. 



There are always, in all species I have thus far examined on this 



13* 



