GENUS OURAMCEBA— OUliAMCEBA VORAX. 67 



OURAMCEBA VORAX. 



Plate IX, figs. 1-12. 



Amoeba xillosa (Wallich). Archer : Jour. Proe. Dublin Micros. Club, 1866, 56, 65 ; Quart. Jour. Mic. Sc. 



vi, 1866, 190, 267 ; x, 1870, 305. 

 Amoeba with remarkable posterior linear processes. Archer: Jour. Proc. Dublin Micr. Club, 1873, 314; 



Quart. Jour. Mic. Sc. xiv, 1874,212. 

 Ouramecba rorax. Leidy : Pr. Ac. Nat. Sc. Phila. 1874, 78 ; 1875, 127, 414. 

 Ouramaiba lapsa. Leidy: Ibidem, 1874,78. 



Proposed genus Ouramecba (Leidy). Archer: Quart. Jour. Mic. Sc. xv, 1875, 202. 

 Amoeba form, plus a cluster of finger-Wee posterior appendages. Archer: Quart. Jour. Mic. Sc. 1876, xvi,337. 



Animal in all respects resembling the ordinary forms of Amoeba proteus, 

 but in addition provided with a variable number of permanently fixed fas- 

 cicles of long filaments, appended to the habitually posterior end of the 

 body. Filaments permanent cylindrical tubes, in each fascicle emanating 

 from a common stalk, simple, or dividing only from near the root, inarticu- 

 late, mostly blunt at the ends ; fascicles from one to half a dozen or more, 

 often more or less separated, but mostly trailing in a single bunch. 



Size. — Small individual in motion 0.14 mm. long by 0.028 mm. where 

 widest, with caudal filaments from 0.04 to 0.18 mm. long. Individual of 

 spheroidal form 0.14 mm. in diameter; in motion, elongated to 0.33 mm., 

 with caudal filaments to 0.2 mm. long. Individual in movement, of palmate 

 form, 0.3 mm. long, with spread of 0.2 mm , with rays to 0.22 mm. of length. 

 Dendroid individuals to 0.33 mm. long, with spread of 0.14 mm. 



Locality. — Rare. Found only in two localities, spring and pond, on 

 Darby Creek, Delaware County, Pennsylvania. 



The singular amoeboid animal to which I gave the name of Oiiramreba 



vovax I first noticed in May, 1874. It was obtained from the sediment of a 

 spring, in which grows water-cress, near Lansdowne station, on the West- 

 chester railroad. I found the creature the following year in the same 

 spring, and also in a pond, a mile distant, near Kellyville, which dried up 

 the succeeding summer. I have likewise observed specimens of what I 

 suppose to be a second species, first noticed in January, 1875, in material 

 collected from the same spring, and preserved since the preceding autumn. 

 Elsewhere I have not found Ouramoeba. 



When first seen I regarded the animal as an Amoeba proteus dragging 

 after it a bundle of mycelial threads. The recurrence of several individuals 

 led me to examine the animal more attentively, when I came to the conclu- 

 sion that the threads were part of its structure. See figures of pi. IX. 



