360 



DONNELL BROOKS YOUNG 



band-like, with the macronucleus broken into two large pieces 

 and the niicronucleus situated between them (fig. 15). It is 

 situated on the left side of the body. 



Uronychia hinucleata {iiew species) (figs. 4, 5, 6) 



This species is distinguished from the others by the follow- 

 ing characters: Carapace 60 to 80m long, 50 to 55 ^ wide and 

 20 to 35 m thick. Dorsal surface arched and marked with 

 small pits. The anterior end more rounded than truncate. 



Text fig. A Outline drawing of U. setigera, showing the position and 

 arrangement of the peristome cirri. From a stained preparation. 



The posterior cirri differ from those of setigera in that never more 

 than four are present in the right ventral pocket and that they 

 are proportionately much shorter. No cirri originate in the 

 peristome which, as in setigera, extends back for more than half 

 the length of the body. The undulating membranes of the 

 peristome are large and are seen frequently, as they are protruded 

 balloon-like while the animal is swimming. Three of the deU- 

 cate sickle-shaped membranelles are found on the left peristome 

 border. The macronucleus is broken up into from three to five 

 fragments and is in the characteristic position on the left side. 

 Two micronuclei are present, one being located between the two 



