106 University of California Publications. [Zoology 



and anterior process are shorter in robust forms and longer in the 

 more delicate ones. 



The horns have the same proximal curvature as in T. trun- 

 cata, but the major flexure is somewhat farther removed from the 

 midbody. Distally the horns are incurved, and then exhibit the 

 outward curvature near the tips, which is also found in T. ramici- 

 formis. There is some curvature to the left distally in both horns. 

 There are 3-6 irregular tubercles on the outer margins of the 

 horns below the major flexures. The ventral horn is usually a 

 trifle longer than the dorsal one. In length the horns are 1.6-3 

 times the distance between their bases, or 12-40 times their width. 



The anterior process is straight or concave dorsally, the pro- 

 jection from the midbody to the flagellar pore being one-fourth 

 to one-third of its total length. There is usually considerable 

 dorsal curvature in the neck and more or less protuberance of the 

 region of the cytopharynx. The head is subcapitate, with slightly 

 impressed furrow. The transverse lists are low and spreading 

 with 20-24 delicate ribs. The longitudinal lists are salient at the 

 junction with the transverse one, almost decurrent on the neck 

 and again salient as they surround the flagellar pore. A suture 

 spine is found in the left list just posterior to the flagellar pore. 

 The thecal wall is structureless. Pores occur in the tubercles. 



This species is the most common one in the genus at San 

 Diego, but is never abundant as compared with many other Dino- 

 flagellata. It varies in size, in the curvature of the antapicals 

 and the neck and in their length and thickness. The number and 

 location of the tubercles is also subject to considerable variation. 



The nucleus is ellipsoidal and usually located near the poste- 

 rior face of the midbody. An attraction sphere is found on the 

 anterior face of the nucleus. One or two pusules are present 

 along the ventral wall, each with efferent canal leading to the 

 flagellar pore. The chromatophores are small, irregular, almost 

 colorless, with superficial distribution. 



Dimensions: Length, 120 to 185 ii\ distance between knees 

 of antapicals, 70 to 130 /a ; between tips, 60 to 112 fx ; altitude from 

 apex to middle of posterior margin of the midbody, 75 to 110 /a ; 

 altitude from apex to middle of posterior margin of the midbody, 

 75 to 110 ix; altitude of midbody to base of anterior process, 30 



