386 ORDER FLAGELLATA-EUSTOMATA. 



In accordance with the views of Perty and other writers, the type of this genus 

 represents merely a tail-'ess variety of Euglena viridis; its generic and specific dis- 

 tinctness is, however, maintained by Stein. 



Amblyophis viridis, Ehr. PL. XX. FIG. 63. 



Body elongate, subcylindrical or compressed, rounded posteriorly, highly 

 flexible, eight or ten times as long as broad when extended ; the anterior 

 margin obliquely truncate, transparent, apparently bilabiate, perforated by 

 the oral aperture and succeeding tubular pharyngeal tract, the remaining 

 endoplasm coloured bright green ; a red eye-like pigment-spot usually 

 present ; endoplast central, subspherical, several rod-like amylaceous cor- 

 puscles generally developed. Length 1-2 10" to 1-140". 



HAB. Pond and stagnant water, in company with Euglena viridis. 



Amblyophys segyptiaca, Schmarda. 



Body elongate, rounded and widest posteriorly when extended, oval or 

 spherical when contracted ; flagellum equalling the body in length ; eye- 

 like pigment-spot conspicuous ; colour dull green. Length, 1-480" to 

 1-360". HAB. Fresh water, Egypt. (Schmarda.*) 



GENUS III. PHACUS, Dujardin. 



Animalcules free-swimming, persistent in form, mostly compressed and 

 leaf-like, terminating posteriorly in a sharp-pointed tail-like prolongation ; 

 oral aperture terminal, not projecting, followed by a distinct tubular pharynx, 

 giving origin to a single long, vibratile flagellum ; cuticular surface indurated ; 

 endoplasm coloured green, usually enclosing anteriorly an eye-like pigment- 

 spot ; contractile vesicle large, subspheroidal, situated close to the eye-like 

 pigment-spot; endoplast conspicuous, frequently modified as in Euglena, 

 and forming by subdivision one or more large oval sporosacs. Inhabiting 

 fresh water. 



The several forms referred to this genus by Dujardin were originally described 

 by Ehrenberg as species of Euglena, from which they differ essentially in their 

 persistent form and in the more or less indurated consistence of their cuticular layer, 

 which often remains as an empty shell after the dissolution of the enclosed contents. 



Phacus pleuronectes, Mull. sp. PL. XXI. FIGS. 2-5. 



Body obovate, compressed, leaf-like, one and a half times as long as 

 broad, caudal prolongation about one-quarter the length of the body, 

 directed obliquely towards the dorsal aspect ; cuticular surface smooth, or 

 presenting a faintly striate appearance only in its empty state ; endoplasm 

 bright green, often enclosing a large, central, spheroidal, amylaceous cor- 

 puscle ; endoplast spherical, posteriorly located ; contractile vesicle con- 

 tiguous to the eye-like pigment-spot, frequently exhibiting irregularly 

 developed lateral lacunae. Length 1-1200" to 1-480". 



HAB. Stagnant water. 



* ' Denkschrift der Kaiser. Akad. der Wiss. Wien,' 1854. 



