1905.] NATURAL SCIEXCES OF PHILADELPHIA. 673 



and shapes. The aperture is produced into a curving tube, coarsely 

 toothed and not everted at the extremity. It reaches a length of 30 ,u. 

 A cvirious circumstance is that individuals of this description habitu- 

 ally swim in a reverse direction, that is to say, with aperture in the 

 rear. 



Forms with straight aperture-tubes are not wanting, but they are 

 not common in the territory. 



Trachelomonas hispida (Perty) Stein. 



Choetoglena volvocina Ehrenberg. 1833. Abh. Berlin Akad. 

 Chonemonas hispida Perty. 1852. Lebensformen. 

 Trachelomonas hispida Stein. 1878. Infusionsthiere, III. 



Lorica brown, ovoid to long-elliptical, ends equally rounded. Sur- 

 face mostly densely hispid throughout, occasionally nearly smooth. 

 Aperture plane or produced into a short, cylindrical, hyaline tube. 



A common and variable species, presenting all its well-known shapes 

 in the Delaware Valley. A very small, tail-like, hyaline projection is 

 sometimes present on the posterior end. The maximum size attributed 

 to the species by Saville Kent is about the equivalent of 40 ij.. but it is 

 usually much smaller, and mostly about 30 /i. An occasional specimen 

 has measured as high as 42 il 



Trachelomonas caudata (Ehr.) Stein. 



Choetoglena caudata Ehrenberg. 1840. Monatsberichte der Berliner Aizad. 

 Trachelomonas caudata Stein. 1878. Infusionsthiere, III. 



Lorica brown, elongate-ovoid, acuminate posteriorly and produced 

 into a conspicuous, hyaline, tail-like process. Surface densely hispid. 

 Aperture in a long, hyaline, trumpet-form tube with everted and 

 deeply dentate limb. 



A rare species, but occurring in typical form in Tinicum. It is said 

 to reach a length of 52 m. The local specimens measured at most 40 ,«. 

 The spiny ornamentation is precisely like that of T. hispida, but there 

 is never any trouble in distinguishing the two. This species is figured 

 by Perty {Zur Kentniss Kleinster Lebensformen, 1852, Tab. X, fig. 14) 

 under the name of Chonemonas acuminata. 



Trachelomonas obtusa sp. nov. PI. XLI, fig. 3. 



Lorica brown, with straight sides, rounded in front, abruptly conical 

 posteriorly. Surface clothed with short, slender spines. Aperture not 

 produced, bordered by a smooth area. Monad green with red pigment- 

 spot. Flagellum long. 



Lorica 33 p- long, 16 ij. broad. Fresh-water ditches and ponds. 



This species is not rare, but it has not yet been found in any large 

 numbers in a single gathering. It occurs in tidal ditches in Tinicum, 

 44 



