556 PROCEEDINGS OF TH-B NATIONAL MUSEUM. vol.47. 



Grande Reservoir (5), common. The description and notes are based 

 on local material. 



This species forms a strange connecting link between the sessile 

 and the previously described free-swimming species of the genus, 

 which all have vibratile ciHa on the corona, while this has rigid setae 

 like the sessile forms. Its mode of locomotion is as surprising as 

 it is unique. When the animal is fully extended, as in the figure, 

 and a change of location is decided upon, the corona is spread out as 

 far as possible, and, using it as a "floating anchor,'' the foot is con- 

 tracted with a sudden jerk; the corona is then rapidly folded and 

 shot forward by extending the foot to its utmost limits, the jelly- 

 case now acting as anchor. The corona is then unfolded and the 

 same laborious cycle repeated again and again, until the point of 

 destination is reached. 



It is evident that this species is much more closely related to the 

 sessile than to the free-swimming forms and it also appears to 

 unite these two sections of the genus into an inseparable whole. 



ROTARIA NEPTUNIA (Ehrenberg). 



Actinurus neptunius Ehernberg, Abh. Akad. Wiss. Berlin (for 1831), 1832, p. 

 145, pi. 4, fig. 23. 



From a sluggish stream in savannas between Panama and Old 

 Panama, few; pond at Miraflores, back water of Rio Camitillo (12), 

 rare. 



Contracted Bdelloids occun-ed in nearly all the collections; only 

 those species are Hsted, which may be recognized by some structural 

 peculiarity even in the contracted state. 



ROTARIA MACRTJRA (Ehrenberg). * 



Rotifer macrurus Ehrenberg, Abh. Akad. Wiss. Berlin (for 1831), 1832, p. 145, 

 pi. 4, fig. 22. 



Among algae on the rocks in a stream flomng into Gatun Reser- 

 voir, common. 



DISSOTROCHA MACROSTYLA (Ehrenberg). 

 PMlodina macrostyla Ehrenberg, Infiisionsth., 1838, p. 500, pi. 61, fig. 7. 



In a pool near the railroad, between Black Swamp and Gatun (2), 

 few; stagnant pool at Empire (4), few. 



NOTES ON DISTRIBUTION. 



To facilitate comparison and especially on account of its bearing 

 on the origin of the as yet unrecorded rotatorian fauna of Gatun 

 Lake in its present extent, the foUomng hst of the collections from 

 the more important localities, arranged with reference to the Conti- 

 nental Divide, will be of interest. 



