330 Dr. G. J. AUman on the Freshwater Zoophytes of Ireland. 



pliytes which have been described as British, and with the ge- 

 nera just noticed, and some new species which have occurred to 

 me, a synopsis of the genera and species of the freshwater Zoo- 

 phytes of Ireland will stand as follows : — 



Order HYDROIDA. 



Family HYDRAID^. 



Genus Hydra. 



Char. — " Polypes locomotive, single, naked, gelatinous, subcy- 



lindrical, but very contractile and mutable in form ; the mouth 



encircled with a single series of granuliferous filiform tentacula." 



1. H. viridis, 2. H. vulgarisy 3. H.fiisca. 



Family TUBULARIAD^. 



CORDYLOPHORA, nOV. gCU. 



Char. — Polypidom horny, branched, rooted by a creeping tu- 

 bular fibre ; branches tubular. Polypes developed at the extre- 

 mities of the branches, ovoid, bearing the mouth at the distal ex- 

 tremity, and furnished with scattered filiform tentacula. 



Cordylophora lacustris. 



Order ASCIDIOIDA. 

 Family LIMNIADES. 

 Genus Cristatella. 

 Char. — Polypidom free, contractile, locomotive. Polypes is- 

 suing from apertures arranged upon the upper surface ; tentacular 

 disc crescentic. Ova with marginal spines. 

 C. Mucedo. 



Genus Alcyonella. 



Char. — " Polypidom fixed, encrusting or floating in the form 

 of an irregular sponge- like mass, composed of vertical aggregated 

 membranous tubes opening on the surface.^' Tentacular disc 

 crescentic. Ova not furnished with spines. 



A. stagnorum. 



Genus Plumatella. 



Char. — Polypidom fixed, coriaceous, confervoid, tubular, 

 branched. Polypes issuing from the extremities of the branches ; 

 tentacular disc of a crescentic form ; tentacula numerous (about 

 sixty), arranged upon the margin of the disc in a single series, 

 invested at their origin by a membrane. 



1. P. repens. 



2. P. emarginata, nov. spec. — Polypidom cylindrical, closely 

 adherent in the greater part of its extent, but sending off several 



