344 bulletin: museum of comparative zoology. 



similar appearance suggests that skeletal fission has taken place but 

 does not conclusively prove it. Further corroboration is seen in 

 presence of an attachment pore near the distal end of the girdle in 

 Levander's species, which provides for protoplasmic continuity of 

 the type seen in Ceratium (Plate 2, fig. 6) where skeletal fission 

 occurs. That the chain formation is of the usual type has been 

 revealed by an examination of material kindly sent by Dr. Levander. 



GONYAULAX SERIES, sp. nOV. 



Plates 1, 2, figs. 1-4. 



Diagnosis: — A rotund (?) species with hyaline theca free from 

 markings, girdle displaced 1 to 2 girdle widths. Forming chains 

 in schizogony without skeletal fission. 



Description: — Body rotund (?), dorsoventral and transdiameters 

 nearly equal, flattened slightly on ventral face. Epitheca with 

 shoulders sloping more rapidly than hypotheca. Girdle equatorial, 

 descending, displaced distally one to two girdle widths, furrow deeply 

 impressed with thin salient ridges of thecal wall without lists. Ven- 

 tral area scarcely indenting the epitheca, longitudinal furrow widening 

 distally to at least three girdle widths. 



Plate formula not fully known; (?)', (?)•, 6", 6.6"', 1*, 1"". Owing 

 to the non-development of the apical and antapical regions, the num- 

 ber of the apicals (1/ to ?) and anterior intercalaries (l a to ?) is un- 

 known and the relations to the single antapical are not revealed. We 

 interpret the rhomboidal plate anterior to the flagellar pore (fl. po., 

 Plate 2, fig. 4) as the ventral apical (1') because of its relationships to 

 precingulars 1" and 6" which it separates as in most other species of 

 the genus. The plate contiguous to its anterior right margin is either 

 an anterior intercalary, l a or the distal (passing about the apex in the 

 direction of the flagellum) member of the apical series, the number 

 in which is not shown in any member of the chain. What is appar- 

 ently apical 2' (labelled 2' (?) in Plate 2, fig. 4) appears only on 

 number six of the chain. There are 6 precingulars (1" to 6", Plate 1, 

 figs. 1 and 2), the typical number for, and exhibiting the typical ar- 

 rangement in Gonyaulax. Plate 6" is quadrangular, as in the G. 

 poly gramma group and others with girdle slightly displaced. The six 

 postcingulars 1'" to 6'", are likewise of characteristic number and 

 arrangement, plate 1"' being a minute linear plate on the left edge of 



