FAMILY PERIDINIACEAE 



29 



left sulcal and the left accessory sulcal lists form the 

 functional left sulcal list. They are very broad, about 

 1.5 girdle widths wide, except at their point of junction, 

 where they are constricted to 0.7 girdle width. Posteri- 

 orly, the left accessory sulcal list extends as a free sail 

 about 1.5 girdle widths long. These two lists extend 

 more or less laterally over the sulcus, covering all its 

 left half and tl\e flagellar pore. Right sulcal list very 

 small. Posterior sulcal list well developed medially, 

 having a width of about 0.7 girdle width, but rapidly di- 

 minishes anteriorly as it runs up the sides of the sulcus 

 The right accessor y sulcal list (ras) is thick and nar- 

 row, overhangs the flagellar pore on its right side, and 

 continues posteriorly to the posterior sulcal plate, form- 

 ing a trough with the posterior accessory sulcal plate. 

 There is no posterior accessory sulcal list. 



" Spines ." Solid antapical spines end antapical 

 horns. They are about 2 girdle widths long; the right 

 is slightly longer than the left. Cursory examination of 

 intact specimens in ventral view shows a spine posteri- 

 orly at each side of sulcus. Spines are simply optical 

 effects produced by the greater absorption of light at 

 points where line of vision falls on tangents of the cur- 

 vature of the posterior sulcal lists. Lists are difficult 

 to see because of transparency, except at these spines. 



Comparisons . Peridinium crassipes is distin- 

 guished from other species of Metaper idinlum by its 

 short, broad body and by its short horns. 



It is of particular interest to compare the ventral 

 area of P. crassipes with that of P. depressum and that 

 of P. truncatum . since crassipes has a structure which 

 in some respects is transitional between the latter two 

 species. The margins of the ventral area are similar to 

 those in P. truncatum . The body sutures have the same 

 relation to those of the ventral area as in that species. 

 The tabulation of the ventral area is transitional be- 

 tween P. depressum and P. truncatum . The largest 

 plate of this area, the right sulcal, is raised so that it 

 forms part of the body proper, as in P. truncatum . On 

 the other hand, the region immediately surrounding the 

 flagellar pore agrees well with P. depressum . There 

 are internal structures at the anterior and posterior 

 ends of the pore. A semilunar structure occurs at the 

 right edge of the pore on the internal surface of the right 

 sulcal plate. This structure is composed partly of an 

 internal plate, the right internal sulcal plate, as in P. 

 depressum. The very small posterior accessory sulcal 

 plate is probably homologous to the similar plate in P. 

 depressum and the larger plate of the same name in P. 

 truncatum . 



The sulcal list system is also transitional between 

 P. depressum and P. truncatum . The right accessory 

 sulcal list ends at the posterior end of the right sulcal 

 plate, as in P. depressum ; it does not join with any pos- 

 terior accessory list as is the case in P. truncatum . 

 The course of the left accessory sulcal list is as In P. 

 truncatum . Otherwise the lists of the posterior region 

 of the sulcus are quite different from those in that spe- 

 cies and are similar to those in P. depressum . There 

 is no posterior accessory list connecting the right and 

 left accessory lists, and the left accessory list extends 

 posteriorly as a free lobe. 



Historical . Kofoid (1907a) described this species 

 from the neritic plankton off San Diego, California. 



Paulsen (1908) considered figs. 43, 1-2 of Schutt 

 (1895) to represent this species, but in our opinion this 

 is uncertain. The side view (fig. 43, 2) might well be P. 



crassipes . but the dorsal view (fig. 43,1) does not show 

 sufficient expansion in the girdle region. 



The antarctic form reported by Peters (1928) is 

 distinctly different from the northern form, but Peters 

 considers the two forms to fall within the limits of a 

 single species. The antarctic form has a peculiar an- 

 gularity of the body and thickness of antapical horns not 

 found in the northern form. 



Jorgensen (1913) separated P. curtipes from P. 

 crassipes , on the basis of its yellow, instead of pink, 

 color; its greater expansion in the girdle region, and 

 the shape of the girdle on the left ventral side. Lebour 

 (1925) accepted this species of JOrgensen but Peters 

 (1928) rejected it. Peters pointed out that species of 

 Peridinium cannot be distinguished by their color, as 

 this is variable. He also was of the opinion that the 

 shapes of the body and girdle are indistinguishable in P. 

 curtipes and P. crassipes . Matzenauer (1933) accepted 

 P. curtipes and figured a specimen with even greater 

 expansion of the girdle region than that of Jorgensen's 

 species, and with short, conical, divergent antapical 

 horns. 



Since both these species have been very inadequate- 

 ly figured, and especially since very little is known re- 

 garding any morphological feature of P. curtipes , it is 

 not possible at this time to pass a proper judgment on 

 the authenticity of P. curtipes . 



The ventral area of P. crassipes had not been ana- 

 lyzed until the present investigations. Kofoid's (1907a) 

 figures show that certain parts of the area are promi- 

 nent and on a level with the main body plates, but even 

 the main features of the area are omitted and the flagel- 

 lar pore is erroneously indicated at the anterior end of 

 the ventral area. 



Distribution . Peridinium crassipes is probably 

 widespread. If we consider Jorgensen s P. curtipes as 

 Peters (1928) suggested, we have records of occurrence 

 from all parts of the Atlantic (Lebour, 1925). Under the 

 name P. crassipes , it was reported from the Antarctic 

 by Peters (1928), and from the Indian Ocean by Matzen- 

 auer (1933), and from the Mediterranean by Forti (1922) 

 and Issel (1928). In the Pacific it was reported from San 

 Diego, California, by Kofoid (1907a), and from the east- 

 ern Pacific, between Hong Kong and Shanghai, by Bohm 

 (1936). 



The Carnegie collection furnishes many new locali- 

 ties for this species in the Pacific, viz., 50 widely scat- 

 tered stations in the tropical and subtropical regions 

 (fig. 38). There are 107 records of occurrence; 63 rare 

 and 44 occasional. It was found about equally at the 

 three levels, with 30 records for the surface, 39 for 50 

 meters, and 38 for 100 meters. There are 14 pump rec- 

 ords and 93 net records. The species was found in both 

 hemispheres in all months of the year except June, July, 

 and August. The records of "occasional" are scattered 

 irregularly over its range. 



The Carnegie records of P. crassipes are limited 

 entirely to the Pacific. In the eastern Pacific it was not 

 found north of Guam, whereas in the western Pacific it 

 occurred as far north as latitude 33° north and as far 

 south as latitude 40° south. 



The surface temperatures at the stations where the 

 species occurred at any depth varied from 15°.0to28°.6C. 

 The ranges of hydrographic conditions in situ were as 

 follows: temperature, 10°.8 to 28°.3 C; salinity, 31.6 to 

 36.4 o/oo; pH, 7.76 to 8.47; phosphate, 3 to 159 mg 

 P04/m3. 



