BRYOZOA 



263 



lophophore ; statoblasts elliptical, without marginal hooks but with a float : 

 several genera. 



Key to the genera of Plumatellidae here described : 



Oj Statoblasts oval ; zooids uniformly spaced 1. PLUMATELLA 



Oj Statoblasts lenticular ; zooids grouped at intervals 2. LOPHOPUS 



1. PLUMATELLA Lamarck. Colony consists of cylindrical, more or 

 less branched tubes, either recumbent or erect, which lie extended on 

 the substratum or form a clump ; 40 to 60 tentacles : about 20 species, 3 

 American ; in ponds and streams, usually not in the light ; the commonest 

 fresh-water bryozoans. 



P. princeps Kraepelin (P. diffusa Leidy) (Fig. 431). Colony creep- 

 ing or erect, often much branched, the branches sometimes fused to- 



Fig. 431 



Fig. 432 



Fig. 431 Plumatella princeps. A, a colony (Davenport) ; B, a floating statoblast; 

 C, a stationary statoblast (Siissw. F. Deut.). Fig. 432 Plumatella polymorpha. 

 A. a colony (Davenport); B, a floating statoblast; C, a stationary statoblast 

 (Siissw. F. Deut.). 



gether; cuticula brown, with a keel that broadens at the aperture; 

 statoblast elongated: cosmopolitan. 



P. polymorpha Kraep. (P. nitida Leidy; P. arethusa Hyatt) (Fig. 

 432). Colony creeping or erect, often richly branched; cuticula usually 

 transparent, rarely brown or keeled ; statoblast nearly 

 circular, sometimes with angular margin: cosmopol- 

 itan. 



P. punctata Hancock (P. vesicularis Leidy; P. 

 vitrea Hyatt) (Fig. 433). Colony creeping, often 

 thickly branched; cuticula colorless, transparent, the 

 elevated mouth cone being wrinkled and spotted with 

 white; statoblast nearly circular: in America and 

 Europe. 



2. LOPHOPUS Dumortier. Colony thick, erect, 

 and sometimes lobed; cuticula gelatinous; about 60 tentacles; statoblast 

 with acute ends; 1 American species. 



L. cristallinus (Pallas) (Fig. 434). Colony up to 10 mm. long: in 

 ponds and slowly-flowing streams, chiefly on water plants; rare; America 

 and Europe. 



Fig. 433 Fig. 434 



Fig. 433 Stato- 

 blast of Plumatella 

 punctata (Siissw. F. 

 Deut). Fig. 434 

 Statoblast of Lopho- 

 pus crystallinus 

 (Siissw. F. Deut.). 



