Chapter 35 

 Order 1 Holotricha Stein (continued) 



Suborder 4 Hymenostomata Hickson 



Cytostome not connected with peristome Family 1 Frontoniidae 



Oytostome at end or bottom of peristome 



Peristome sickle-form, ciliated slit; sunk at right angles to body surface 



Family 2 Ophryoglenidae (p. 617) 



Peristome long, begins at anterior end of body 



Peristome with a one-layered membrane which forms a pocket sur- 

 rounding cytostome on right edge and a row of cilia or mem- 

 brane on left Family 3 Pleuronematidae (p. 618) 



Peristome otherwise 



Peristome with 2 one-layered membranes; no distinct ectoplasmic 

 pocket around cytostome. .Family 4 Cohnilembidae (p. 620) 

 Peristome furrow either covered densely with cilia, besides an un- 

 dulating membrane on right edge, or with only a thick undu- 

 lating membrane on the right edge 



Family 5 Philasteridae (p. 621) 



Family 1 Frontoniidae Kahl 



Genus Frontonia Ehrenberg. Ovoid to ellipsoid; anterior end more 

 broadly rounded than posterior end; flattened; oral groove lies in 

 anterior third or more or less flattened ventral surface, to right of 

 median line; lancet-like with pointed anterior and truncate poste- 

 rior end; left edge is more curved than right edge, and posteriorly be- 

 comes a prominent ectoplasmic lip; cytostome with a complex or- 

 ganization (on left edge a large undulating membrane composed of 

 3 layers, each being made up of 4 rows of cilia; on right, semi- 

 membranous groups of cilia; 3 outer rows of cilia from the postoral 

 suture; along this suture ectoplasm is discontinuous so that large 

 food matter is taken in; with a small triangular ciliated field poste- 

 rior to cytostome and left of suture); a long narrow postoral groove 

 which is ordinarily nearly closed; cytopharynx with numerous strong 

 fibrils; ciliary rows close and uniform; ectoplasm w4th numerous 

 fusiform trichocysts; macro nucleus oval; one to several micro nuclei; 

 1-2 contractile vacuoles, with collecting canals and an external pore; 

 fresh or salt water. Bullington (1939) recognizes 14 species. 



F. leucas E. (Figs. 22, a, h; 288, a). 150-600^* long; fresh water. 



F. branchiostomae Codreanu (Fig. 288, b). 75-1 00m by 55-95ju; 

 commensal in the branchial cavity of Amphioxus. 



Genus Disematostoma Lauterborn. Somewhat similar to Fron- 

 tonia; pyriform; with broadly rounded, truncate or concave anterior 



608 



