MORPHOLOGY AND PHYSIOLOGY OF GENUS URONYCHIA 357 



Kent C'Sl), following Stein ('59), defines the genus in these 

 words: ''Body oval, encuirassed, turgid, the sides rounded, trun- 

 cate in front with a prominent membranous upper lip. The 

 hinder extremity having developed on the ventral side two con- 

 verging bow shaped fissures into which the short claw shaped 

 anal and marginal uncini or styles are inserted; ordinary ventral 

 or frontal styles entirely absent; the peristomial evacuation pocket 

 shaped, closing sphincter-wise at will, its inner or right hand 

 border bearing a band shaped undulating membrane." 



Although this description holds in general, it is not correct in 

 some points. The membranous upper lip is not found in all 

 species and Kent's own figures (figs. 9, 10) fail to show it. At 

 times the undulating membranes of the peristome protrude in 

 front, and it may have been this which was seen. From the 

 study of the living animal it is difficult to determine whether 

 the posterior cirri are inserted in two ventral pockets or whether 

 some are in a third pocket which is on the dorsal side. Stained 

 preparations (fig. 14) confirm Maupas when he writes, ''Stein 

 place encore dans cette serie (i.e., with the ventral posterior 

 cirri) les trois gros appendices de la region posterieure de bord 

 droit de ces memes Infusoires. Mais c'est la une erreur; car 

 ces appendices sont separes des cirres transversaux par une mince 

 lamelle prolongement de I'extremite posterieure ou caudale du 

 corps par consequent appartiennent a la face dorsale ainsi que 

 Claparede et Lachman I'avaient deja bien reconnus." The 

 cirrus-like membranelles are somewhat differentiated into a 

 central and two lateral groups. Ordinarily the central group is 

 the one most easily seen. The lateral ones bend in towards the 

 center and partially close the anterior end of the peristome. Oc- 

 casionally they spread out, and it is their movement as they open 

 and close over the end of the peristome that accounts for the 

 appearance of the sphincter-wise closing of the peristome. 



Only two species have been described for the genus, Uronychia 

 transfuga (0. F. M.) and U. setigera (C). This first is defined 

 by Kent ('81), following Stein ('59), thus, "Body ovate, trun- 

 cate in front, slightly narrower posteriorly, more usually ob- 

 Uquely truncate, angular and bent toward the left, but somewhat 



