174 bulletin: museum of compaeative zoology. 



The hypotheca is very short, scarcely a transdiameter in axial length. The 

 left antapical is long, nearly equalling the altitude of the epitheca in length. It 

 is curved more or less evenly to the left and dorsally. The right antapical is 

 short, straight, a little more than a transdiameter in length, subparallel to the 

 left horn or divergent. 



Length, 270-350 /x ; transdiameter at girdle, 35-40 /i. 



Stations, 4709-4736. 



Peridiniuin fatulipes, sp. nov. 



Plate 5, Fig. 30. 



A medium-sized species of the P. divergens group characterized by its widely 

 divergent, heavily reticulate antapicals with wide postmargin. It differs from 

 P. elegans in its more divergent, widely set antapicals, and from P. grande in 

 these same particulars, and also in its smaller size and in the peculiar distribution 

 of its minute pores. 



The body is elongated, its length 1.6 times the transdiameter and 2.5 times 

 the dorso-veutral. Epitheca equals the hypotheca, both ventrally excavated. 

 The epitheca resembles that of P. grande in proportion, having deeply concave 

 lateral faces and long attenute apical horn. 



The hypotheca is contracted to 0.5 of the transdiameter, above the level of the 

 base of the antapicals, which are slender, tapering, and widely divergent, their 

 length 0.4 of a transdiameter, and the distance between their tips 0.8-0.9 of a 

 transdiameter. The postindentation is 0.3 of a transdiameter in depth, forming 

 a broad arc, notched by the longitudinal furrow, as seen ventrally. 



The girdle is narrow, slightly impressed, with low membranous ribbed lists, 

 with little displacement or forming a slight ascending right spiral. Longitudi- 

 nal furrow with high lists not projecting posteriorly beyond the postmargin. 



Plates normal, three in middorsal series. Sutures with very broad bands of 

 intercalary striae. Plates centrally reticulate with minute subequal irregular 

 polygons, with minute pores irregularly distributed, not centrally located in 

 the polygons, and not in the mesh itself. 



Length, 147 jj. ; transdiameter, 100 ft. 



Station, 4732. 



Peridinium grande, sp. nov. 



Plate 5, Pig. 28. 



A very large species of the P. divergens group with wide flaring girdle and 

 long horns. 



Body elongated, length 1.2-1.4 times the transdiameter and 2-2.3 times the 

 dorso- ventral. Epitheca equals the hypotheca, girdle section very broadly 

 reniform. Epitheca a very low cone with very flaring base, and dorsally set 

 tapering apical horn, its altitude 0.6 of its transdiameter. Sides deeply concave. 



Hypotheca less abruptly contracted than the epitheca, its transdiameter at 

 base of the horns 0.33-0.4 of that at the girdle. Its altitude is 0.66-0.75 of 



