NO. 2164. REVISION OF ROTATORIAN GENERA— EARRING. 565 



tween these two ridges there is a deep groove of semicircular cross 

 section passing from side to side of the ventral plate. This groove 

 is narrowest and deepest on the median line, and becomes wider and 

 shallower as it approaches the sides of the body. The dorso-ventral 

 depth of the body varies from one-half to two-thirds of the length. 



Tlie anterior margin of the lorica is curved very slightly in its 

 upper portion and quite strongly in the region of the ventral sinus. 

 While it has the appearance of being smooth, it is in reality very 

 minutely denticulate; as this denticulation is quite beyond the 

 possibilities of the halftone process without excessive magnification, 

 it has not been indicated hi the illustrations. The dorsal sinus is 

 narrowly V-shaped, slightly rounded posteriorly, and its depth is 

 one-fourth the length of the lorica. The ventral sinus is broadly 

 semielliptic and its edges slightly outcurved, to give the necessary 

 freedom for the head and coronal cilia. 



The foot opening is ovate and pomted posteriorly; the length is 

 one-fourth the length of the lorica and the width about two-thirds 

 of its length. The foot is moderately long and the basal portion 

 quite stout; the posterior segment bearing the toes is slender and 

 well definded; anterior segments are mdistinct, but probably two 

 are present. The toes are stout at the base and taper fairly rapidly 

 for one-half their length, ending in slender, acute points; their length 

 is one-fifth the length of the body. 



Total length, 160 fx; length of lorica 120 /x, width 75-80 fi, dorso- 

 ventral depth, 55-70 /x; transverse width of anterior opening, 32-35 /z; 

 depth of dorsal sinus, 20 /z, of ventral sinus, 21 /x; length of foot 

 opening, 34-36 n, width, 24 (j.; length of foot, 30 fi, of last joint, 12 /x; 

 length of toes, 24 fi. 



The differences between Loph,ocliaris salpina and L. oxysternon 

 are so slight that one description is almost a repetition of the other. 

 Both are variable to a considerable extent, especially in dorso-ventral 

 dimensions; perhaps L. oxysternon is the more variable, at least such 

 are the indications of the material examined. On the other hand, 

 this seems to be by far the more common species and there was con- 

 sequently a better opportunity to ascertain the limits for this form 

 than for the comparativel}^ rare L. salpina, known to the writer 

 from local collections only. The following characteristics only may 

 be depended on as distinctive: For L. salpina — (1) The angulate 

 anterior margin with distinct dorsal and ventral sinus, the truncate 

 portion bemg coarsely denticulate; (2) the transverse plication of 

 the dorsal keel; and (3) the absence of a transverse groove on the 

 ventral plate. For L. oxysternon — (1) The rounded anterior margin, 

 merging graduaUy with the dorsal and ventral smus, denticulation 

 excessively minute; (2) the absence of transverse plications on the 

 dorsal keel; and (3) the deep transverse groove in front of the foot 

 opening. In all other respects they appear to be identical. 



