176 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



margin. It is excavated ventrally, and its left lateral face is nearly straight 

 while its right one is concave. Its altitude, excluding spines, is 1.2-1.35 

 transdiameters. Antapical horns are not developed, but from the postangles 

 arise two subequal, solid, acicular, finned spines which are slightly divergent. 

 Their length is 0.2-0.45 of a transdiameter. 



The girdle is postmedian ) the transverse furrow is not indented, and forms 

 an ascending right spiral displaced distally less than its width. It has hyaline 

 ribbed lists. The longitudinal furrow reaches the postmargin, is expanded 

 distally, but its low lists do not as a rule project beyond the postmargin. 



Sutures with striate intercalary bands, surface of plates sparingly porulate. 



Length, 60-105 fx ; transdiameter, 50-85 /x. 



Stations, 4613, 4711. 



Peridinium murrayi, sp. nov. 



Plate 5, Fig. 29. 



Syn. P. divergens, Ehrbg. in Murray and Wlritting ('99), PL 29, Fig. 4. 



A large species resembling P. oceanicum, but differing from it in the much 

 lower epitheca with more concave sides, longer apical horn, and longer and 

 more divergent antapical horns. 



Body compressed dorso-ventrally, dorso-ventral diameter 0.65 of the trans- 

 diameter, and about equal to the length of the apical, or either of the antapicals. 

 Distance between the tips of the antapicals equals or exceeds the transdiameter. 



Girdle nearly median, furrow not impressed, with high membranous ribbed 

 lists, forming a descending right spiral displaced twice its width. Longitu- 

 dinal furrow with high lists which project beyond the postmargin. 



Chromatophores radiating, linear. 



Length, 250 /x; transdiameter, 135 /x. 



Station, 4736. 



*■> 



Peridinium tenuissimum, sp. nov. 



Plate 5, Fig. 34. 



A minute hyaline species related to P. pedunculatum, but distinguished by 

 its smaller size, more elongated body, and longer apical horn and antapical 

 spines. 



The length of the midbody excluding horn and spines exceeds the transdi- 

 ameter. The midbody is broadly ovoid, passes abruptly into the cylindrical 

 apical horn, whose length is but little less than a transdiameter. It flares 

 slightly at the apical pore. The acicular divergent antapicals are nearly a trans- 

 diameter in length. The girdle is median on the midbody and is not displaced. 

 The lists of the longitudinal furrow extend beyond the postmargin. The 

 whole organism is exceedingly hyaline, plates and sutures not determinable. 



Length, excluding antapical spines, 45-50 fi ; transdiameter, 25-28 p. 



Station, 4711. 





