Vol. LX, No. 1.| Sponges of the Lake of Tiberias. 61 
a4 
To the subfamily Potamolepidinae I assign the following 
genera :— 
Nudospongilia (gen. nov.), Pachydictyum, Weltner, Corti- 
sg bea (gen. nov.) and Potamolepis, Marshall. Whether or 
i) s Metschnikowia'! should be associated with these 
Santa is "doubtfal. 
e two new genera are described below, being represented 
by species from the Lake of Tiberias, and in the third section 
prove of use in distinguishing all these genera. — The names of 
mules, are Gasikbed 3. the names of those genera in whieh 
gemmules are kiows oe occur are marked with | an asterisk. 
Key to certain genera of Freshwater Sponges. 
Minute birotulate microscleres present 
in the parenchyma. (Sponge hard; 
skeletal fibres as a rule somewhat ill- 
defined ; neonate stout vertical 
fibres sometimes present). . -. [Corvospongilla.*| 
Il. No microscleres 
trace of a subdermal cavity 
or of efferent grooves under 
the dermal membrane in th 
neighbourhood of the oscula. 
(External membrane delicate; 
~ 
i ise in strong chitinous 
substance) . (Veluspa.*) 
200A subdermal cavity “usually pre. 
sent effer ubderma 
grooves as a mp well ee 
oped. 
A. Athick chitinized external 
membrane present. 
bres similar; sponge o 
stony hardness) [Uruguaya.*} 
B. External membrane delicate. 
A The aisahige’ s s originat daanion is not atailabies but canes genus is 
redescribed by Dybowski in the paper ci ited in the bibliography opposite 
his name. 
