36 Transactions of the Society. 



European observers, but tbese members of the genera have thus far 

 been observed only m that part of America occupied by the United 

 States, over which they are doubtless widely distributed. It has seemed 

 preferable to describe their characters as concisely as possible, rather than 

 to occupy space by the refinements of rhetoric, and so complicate sub- 

 sequent reference and comparison. 



Tetraselmis limnetis sp. nov., plate V. fig. 1. 



Lorica broadly oval, the length but slightly exceeding the width, both 

 extremities evenly rounded ; body of the inclosed zooid almost entirely 

 filling the cavity of the lorica, the endoplasm green, granular, with a 

 small, colourless, transparent spot at the anterior border ; flagella four, 

 each exceeding the lorica in length ; contractile vesicles two, small, 

 situated one on each side of the frontal clear space ; nucleus not observed ; 

 a large, subspherical amylaceous corpuscle posteriorly located. Length 

 of lorica 1/1800 in. Habitat, pond water. 



This is only the second known species of the genus. 



Petalomonas pleurosigma sp. nov., fig. 2. 



Body suboval or ovate, depressed, less than twice as long as broad, 

 widest centrally, tapering towards both extremities, the anterior margin 

 narrowly rounded, the posterior prolonged as a short, obtuse acumina- 

 tion ; lateral borders more or less sigmoid ; dorsal and ventral surfaces 

 each traversed by a narrow, subcentral, longitudinal depression or furrow, 

 which usually do not extend into the caudal acumination ; oral fossa dis- 

 tinct, the flagellum apparently originating from one of its walls, and 

 exceeding the body in length, the distal extremity alone undulating ; 

 nucleus and contractile vesicle distinct, situated opposite each other near 

 the lateral margins of the anterior body-half Length of body 1/1500 in. 

 Habitat, standing pond water. 



In the double sulcation of the flattened surfaces this form resembles 

 Petalomonas disomata Stokes, but is readily distinguishable by the 

 posterior acumination, the sigmoidal lateral margins, and the smaller 

 size. 



The writer, in the ' Annals and Magazine of Natural History ' for 

 February li^86, described an infusorian under the title of Paramonas 

 alata, with a diagram. It is scarcely necessary to state that the generic 

 name should have been Petalomonas, as the indurated and carinated 

 cuticular surface at once relegate the animalcule to the latter position. 



Chloropeltis monilata sp. nov., fig. 3. 



Body broadly ovate or subcircular, strongly compressed, about one 

 and one-half times as long as broad ; general cuticular surface not ribbed 

 but entirely covered with conical, rounded elevations arranged more 

 or less in longitudinal series ; caudal prolongation straight or slightly 

 curved, forming less than one-fourth the length of the entire body ; fla- 

 gellum not exceeding the zooid in length ; eye-like pigment-spot usually 

 present ; contractile vesicle conspicuous, anteriorly located. Length of 

 body 1/650 in. Habitat, standing pond water. 



This conspicuously differs from Ch. liispidula (Eichwald) Stein (the 



