new Forms of American Rotifera. 25 



nearly straight, the alvine being somewhat the shorter 

 (fig. 17), and all shorter than those of S. similis. The sinus 

 between the posterior spines (fig. 17) shows a rather con- 

 spicuous bulging, while in Salpina sunilis the sulcus is 

 entirely even and evenly rounded. The front is likewise 

 more evenly rounded (fig. 18), with a more decided bulging 

 at or near the buccal orifice. Internally the only apparent 

 diiFerences are the smaller contractile vesicle of tlie variety 

 and the strong internal ciliation of the oesophagus, instead of 

 the conspicuous flagella as with S. similis, the oesophageal 

 cilia of the variety scarcely differing from those of the 

 stomach, and not extending into that organ as an undulating 

 fascicle. The granulations of the anterior lorical collar are 

 coarser and fewer than those of the same part on Salpina 

 similis. These points of difference are hardly sufficient to 

 warrant the describing of these specimens as a new species. 



Rattulus palpitatus, sp. n. (PI. VIII. fig. 19.) 



Lorica subcylindrical, widest anteriorly, somewhat tapering 

 posteriorly, both extremities truncate, but in opposite direc- 

 tions ; toes curved, continuing the general curvature of the 

 lorica, tapering, acute, about one fourth as long as the body ; 

 basal stylet apparently none ; dorsal contour of the lorica in 

 lateral view closely approximating the segment of a circle ; 

 brain not opaque, large, broadly ovate, bearing at its poste- 

 rior extremity a large red papilliform eye-spot ; mastax 

 large, the trophi unequal ; gastric glands dorsad to the frontal 

 region of the stomach and apparently united into one ; ovary 

 large, ventrad to the ciliated stomach and to the intestine ; 

 contractile vesicle small, near the posterior extremity of the 

 lorica, in the median line, and pulsating at the rate of about 

 forty contractions per minute, the cloaca being forced open 

 for a short distance at each pulsation. 



Length of the extended body, exclusive of the toes, about 

 -jI^ inch ; greatest lateral width (height) near the middle of 

 the lorica and about ^^ inch. 



The species is remarkable on account of the rapidity with 

 which the contractile vesicle pulsates, the number averaging 

 about forty each minute when the animal's movements are 

 but slightly restricted and when it seems to be well and at 

 ease ; when it is held by the pressure of the cover-glass the 

 pulsations become irregular. 



The toes I have not seen separated. 



It is not easy to retain the curved and rigid body so that 

 either a direct dorsal or ventral view may be obtained, but 



