790 ORDER HYPOTRICHA. 



Genus XXII. ACTINOTRICHA, Colin. 



Animalcules free-swimming, slightly flexible, ovate or elliptical, the 

 anterior border of the ventral surface bearing five or six abnormally thick, 

 sharply-pointed frontal styles, a row of smaller styles produced down each 

 lateral margin, and a transverse row of five or six anal styles developed at 

 the posterior extremity ; adoral row of cilia very large, uncinate. 



Actinotricha saltans, Cohn. Pl. XLV. Fig. 6. 



Body elliptical, equally rounded at both extremities, about twice as 

 long as broad ; the five large frontal styles radiating symmetrically from the 

 anterior border, the central style the largest, and the remaining ones gradually 

 diminishing in size backwards ; eight or nine smaller styles entering into 

 the composition of each of the latero-ventral rows, the four posterior styles 

 in each row being about twice the length of the preceding four ; anal styles 

 long and stout, six in number, equal in size, forming an even transverse series, 

 often branched at their distal terminations ; peristome and adoral cilia 

 produced backwards to a distance of about one-third of the length of the 

 entire body ; parenchyma transparent, colourless. Length 1-360". 



Hab. — Salt water, swimming evenly in a straight line, springing or 



creeping. 



It is difficult to decide whether the latero-ventral series of seta represented by 

 Cohn in his description and illustration of this species, belong rightly to the ventral 

 or to the marginal series; the author is inclined, however, to believe that they appertain 

 to the latter, and that the true ventral and probably also the frontal styles have been 

 overlooked. Should this inference prove correct, this single generic type, excepting 

 for the abnormal development of the six frontal styles, is closely allied to Stylonychia. 



Genus XXIII. STYLONYCHIA, Ehrenberg. 



Animalcules free-swimming, persistent in shape, encuirassed, ovate or 

 elliptical ; peristome-field extensively developed, its reflected inner border 

 finely ciliate, usually bearing a band-like undulating membrane ; anterior or 

 frontal styles usually eight in number, occupying a more or less distinct 

 circular area ; five claw-like ventral styles or uncini, and five straight anal 

 styles ; the marginal setae forming on each side an even and continuous 

 border ; three long, hair-like caudal setae usually developed at the posterior 

 extremity ; endoplasts two in number, oval or elongate, sometimes cylin- 

 drical or bacillar, dividing into separate ovate nodules ; contractile vesicle 

 single, spherical, situated near the posterior angle of the peristome. 

 Inhabiting salt, fresh, and stagnant water. 



Stylonychia mytilus, Ehr. Pl. XLV. Figs, i and 18-22. 



Body elongate-elliptical, more than twice as long as broad, rather wider 



anteriorly, with a slight left curvature, tapering backwards from the centre, 



the posterior third frequently becoming abruptly narrowed and bent 



towards the left, the posterior termination mostly truncate ; peristome- 



