178 PROCEEDINGS OF THE ACADEMY OF [1887. 



Colony cushion-like, rarely branched, bright green, yellow, 

 yellowish-brown or white, with large osculse, which lead to a system 

 of small canals. The skeleton spicules are either entirely smooth or 

 entirely rough or both forms are found together in the same colony. 

 Their degree of roughness is very different, as the spines are some- 

 times quite indistinct, at others very conspicuous. The spicules are 

 either straight or slight!)^ curved ; sharp pointed and fasciculated 

 within a hornv sheath. The gemmules are surrounded Avith shallow 

 apertures, slightly flattened from above downward through air-cham- 

 ber-layers of greater or less depth. Amphidiscs numerous; ordinarily 

 in a single layer, but sometimes in two layers {E. amphizona) and 

 occasionally in three layers (>S'. mirabilis), set one over the others. 

 In the last case the external layer forms an imperfect or broken 

 series of amphidiscs. The axes of the amphidiscs are short, relatively 

 to their thickness; the rays either smooth or notched on their edges. 



Ephydatia mulleri is known in Euroj)e, in Germany, Bohemia, 

 Russia, Galicia, and England. 



(61 Ephydatia fluviatilis, auct. 



Syn:- 



1788 Spongilla fluviatilis, (?) IJnn. 

 1788 " canalium. (?) " 



1816 " pulvinata (?) Lamarck. 



1842 " fluviatilis (?) Johnston. 



1856 " " Lieberkiilin. 



1863 " ' Bowerbank. 



1867 Ephydatia " Gray. 



1877 Spongilla " Vejdovsky. 



1881 Meyenla " Carter. 



1882 Ephydatia " Dybowski. 



1883 " " Vejdovsky. 



1883 Sporujilla " Retzer. 



1884 Ephijdatia " Wierzejski. 

 1886 " " Petr. 



Amorphous, cushion-like colonies of an emerald, or bright Isabella- 

 yellow color. Skeleton spicules smooth throughout, slightly curved 

 and^sharp-poiuted. Parenchyma spicules (?) also smooth, small 

 and very slightly bent. Gemmulne small, yellow with a thick horn- 

 membrane; the external air-chamber-layer surrounded by a thin 

 chitinous covering. In this layer toothed amphidiscs are embedded, 

 having either smooth or spinous shafts that are constricted in the 

 middle and twice as long as the diameters of the rotulse. 



In Europe E. fluviatilis is found in France, England, Germany, 

 Bohemia, Galicia and Russia. 



