534 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 51. 



moderately developed and probably serve to direct the food to the 

 mouth rather than as organs of locomotion. As such the lateral 

 portions of the circumapical band have become specialized, recall- 

 ing the auricles of the Notommatids. The trophi, plate 93, figures 7 

 and 8, are typically malleate, only differing in the large transverse 

 crutch at the end of the fulcrum. The basal apophyse or, probably 

 more correctly, the first transverse ridge, of the rami is very large 

 and evidently specialized for the attachment of the abductor mus- 

 cles. The unci are five-toothed, the slightly clavate teeth resting 

 in the depressions between the ridges of the rami. 



The males of the Lepadellids are very rarely found; Wesche has 

 described ^ the male of Lepadella ovalis (Miiller) ( = Metopidia 

 solidus Gosse). It is of the usual degenerate type and in appear- 

 ance almost identical with the male of L. patella (Miiller), plate 91, 

 figures 1 and 2. 



The majority of the species belonging to this genus vary between 

 rather wide extremes; the variations are, however, heritable, in 

 contradistinction to the cyclic, seasonal or ecologic variations ex- 

 hibited by many Rotatoria. Consequently we find each species 

 broken up into a number of local races, varying but little individu- 

 ally, so that, in order to estabhsh the limits, it is not sufficient to 

 examine the form which happens to exist in a circumscribed terri- 

 tory, but it is important to have material from the greatest possible 

 number of stations. It will readily be understood from this, that 

 when some rare species, of which the description given here is based 

 on material from one or two collections, is found elsewhere, it is 

 quite likely to possess a number of pecufiarities. The most reliable 

 characteristics are the relative longitudinal dimensions, such as the 

 depth of the dorsal and ventral sinus, the length of the foot groove, 

 foot and its terminal joint, and, finally, the length of the toes. Pro- 

 portional measurements given in the text have therefore been re- 

 ferred to the length of the lorica. Transverse measurements, such 

 as the width of the lorica, anterior opening and the width of the 

 foot groove are all subject to considerable variation and therefore 

 rather unreliable. 



The genus seems naturally divisible into two groups, a Lepadella- 

 group, having a convex dorsal plate without any median keel, and a 

 Metopidia-group with a dorsal keel, making the cross section of the 

 body triradiatc or trialate. The Lepadella-group would under this 

 arrangement be composed of the following species : Lepadella apsida, 

 new species, L. ovalis (Miiller), L. patella (Muller), L. latusinus 

 (Hilgendorf ) , L. amphitropis, now species, L. quinquecostata (Lucks), 

 L. cryphaea, new species, L. acuminata (Ehrenberg), L. dactyliseta 

 (Stenroos), Lepadella henjamini, new species, L. cyrtopus Harring, 



* Journ. Quekett Micr. Club, ser. 2, vol. 8, p. 123. 



