NO. 21G4. REVISION OF ROTATOR! AN GENERA— BARRING. 533 



some instances really broad, rounded lobes. Nearly all the species 

 have a collar of some sort around the anterior opening ; this may be 

 only a beadlike thickening of the edge of the lorica, or it may take 

 the form of a coarsely stippled area limited posteriorly by a faint 

 line. This stippled collar is usually narrowest on the median line 

 and increases in width toward the edges of the lorica ; the stippling 

 is coarsest near the middle of the collar and disappears gradually 

 as the width becomes greater. 



The foot projects through an opening in the ventral plate, about 

 two-thhds the length of the lorica from the anterior end, and at the 

 bottom of a nearly parallel-sided groove, semicircular in section, 

 which is here called the foot groove. The body projects slightly 

 through the foot opening, forming the base of the three-jointed foot, 

 which bears two slender toes, about one thu-d the length of the lorica. 

 While no doubt good reasons could be advanced for considering the 

 foot four-jointed, it seems natural to apply the term "joint" only 

 to the three posterior segments of the foot, as the basal segment is 

 not mobUe. Moreover, the "foot," as this term is applied to Rota- 

 toria, is in no dase anything but a mere convention for the posterior 

 reduced portion of the body and the starting point is consequently 

 also conventional and not founded upon any morphological dis- 

 tinction. 



On the dorsal side of the terminal foot joint there is a circular 

 depression with a small rounded papilla in the center. This is here 

 called a sensory pit. Whether this is really the true significance of 

 this structure can not be definitely established, but it is at least not 

 improbable, reasoning from analogous organs in other genera. The 

 rounded papilla appears to have a central marking, but no sensory 

 setae have been found on it, in spite of careful search. This sensory 

 pit has not been demonstrated in all the species, but has been found 

 in all cases where it was possible to obtain a properly oriented view 

 under a sufficiently high magnification. 



No detailed study has been made of the corona and the trophi in 

 the different species of the genus, but Lepadella henjamini may 

 serve as an example, especially as these organs apparently vary but 

 little in this genus. The corona, plate 93, figures 5 and 6, is a typical 

 EucUanis-corona with the dorsal arc of cifia suppressed on account 

 of the protective dorsal hood. In Euchlanis the head is protected 

 by three plates — one dorsal and two lateral — none of which projects 

 far enough to interfere with the free movement of the coronal cilia. 

 In Lecane and Monostyla various stages of the progressive develop- 

 ment of the dorsal segment of this head covering are to be found; 

 in Monostyla galeata Bryce it reaches almost the extreme speciahza- 

 tion of the LepadelHds. The buccal plate is covered with very short 

 cilia and the mouth is at its lower extremity; the lateral arcs are 



