104 



A comparison of my results with Paulsen's (: 04) figures reveals 

 some discrepancies in our respective accounts. The small postcingular 

 at the left side of the theca as figured by Paulsen is omitted by me, and 

 the wide postcingular at the right is divided at the angle of the antapical 

 into two plates. I believe Paulsen's figure to be in error in these 

 details. 



The thecal walls are finely reticulate with aréoles 2 — 4 i-i in diameter 

 which do not appear to be porulate. The reticular mesh varies consider- 

 ably in its development in different individuals and in some shows more 

 prominent sublinear longitudinal striae. In the individual shown in the 

 figure the reticulations were very regular and no longitudinal striae ap- 

 peared. On the dorsal side faint traces of broad intercalary bands could 

 be noted on a deep focus on the wall along the suture lines in a few 



Fig. 1. Ventral \devv of fully developed theca of Gonyaulax triacantha. 



Fig. 2. Dorsal view. 



Fig. 3. Diagrammatic lateral view. 1 — 3, apical plates ; 4—9, praecingular plates; 



10 — 13, postcingular plates; 14, accessory; 15, antapical; 16, longitudinal furrow 



plate ; a — f, spines of the hypotheca. Zeiss Apochr. 2 mm. Comp. Oc. 12. X 1000. 



cases. The individuals also vary in the degree of development of the 

 spinous processes of the hypotheca, and in the extent to which the reti- 

 culations extend upon their bases. 



The contraction of the epitheca into the apical horn is very abrupt 

 forming a subhorizontal shoulder in which it is difficult to follow suture 

 lines. This contraction is usually more pronounced than is shown in the 

 figures. The spines of the hypotheca are solid projections often provided 

 with wide smooth or denticulate fins. In fully armed individuals there 



