4 NEW SPECIES OF LIMNIAS — OF EHRENBERG'S GENUS AULISCUS. 



II. 



New Species of Limnias. 

 Eiinsmas annulatus, B. 



(Plate, Fig. 28.) 



Case of the animal having numerous transverse rings. 



In searching, in various parts of the United States, for Desmidieae, my attention 

 was long ago drawn to the frequent occurrence in lakes, ponds, &c. of short cylin- 

 drical membranaceous tubes, closed at one end and marked with rings so as to 

 resemble the trachea of insects. 



The real nature of these bodies remained unknown to me until the summer of 

 1851, when I detected great numbers of similar forms attached to various aquatic 

 plants in pools near West Point, and found them to be the cases of a species of 

 Limnias, not noticed in books prior to the publication of Pritchard's Infusorial 

 Animalcules, second edition in 1852, where may be found, on page 619, the follow- 

 ing description: — 



" Limnias ? appears to be a distinct species which I do not find described. 



The case is ribbed and semi-transparent, and is composed of a series of lateral rings, 

 found in a ditch near Witlingham, Norwich, on duck-weed (Brightwell) ." 



This description leaves no doubt that the species referred to by Pritchard is the 

 same as our own, and as he has refrained from giving it a specifi.c name, I propose 

 to call it L. annulatus. It is the only species which I have yet noticed in the 

 United States, and occurs in vast numbers at West Point, New York, where I have 

 found large plants, such as Ludivigia palusiris, literally covered with the brown 

 cases of these animals ; affording, when the animals, with their rotatory organs, 

 were protruded, an exceedingly beautiful spectacle when moderately magnified. 

 Our figure is only intended to show the form and markings of the case, with the 

 general appearance of the animal, the details of the latter being reserved for further 

 study. 



III. 



New Species of Ehrenberg's Genus Auliscus. 



The generic characters, as given by Ehrenberg, for the genus Auliscus are as 

 follows : — 



" Lorica bivalve, cylindrical (or orbicular), multiplying by perfect self-division; 

 two large (not tubular) apertures on each surface of the disk laterally, which also 

 is not cirrhose. This genus differs from Gerataulus in wanting the eirrhose surface 

 of the lateral disks, as also the tubular apertures." (See PnlcIiarcTs Infusoria, 

 second edition, page 320.) 



Although it has long been known to me that, in most if not all of the cases 

 where Ehrenberg attributes apertures to the shells of Diatomacea'e, no real perfora- 

 tions of the shell exist, I yet failed to perceive, until quite recently, that to the 

 genus Auliscus are probably referable a number of beautiful forms, for which I had 

 intended to propose a new genus with the name of Mastodiscus. I am, however, 



