a et a oe 
Vol, IX, No. 1.] Sponges of the Lake of Tiberias. 67 
[V.S.] 
tems of the kind are found. The subdermal (afferent) her 
is poorly represented or absent, but efferent channels covered 
only by the dermal often be detected in the ieee 
bourhood of the oscula. “Cystocytes are apparently absent. 
Skeleton.—The skeleton consists of well-developed vertical 
fibres crossed at frequent intervals by less well-developed trans- 
verse ones. Near ie external surface the latter fibres are 
greatly thickened so as to form a strong casement or it 
eyond which t feleeined vertical fibres project upwards, su 
porting the dermal membrane, which is not strongly ohitinized, 
but apparently somewhat collenchymato ous. 
Spicules.—In the only known species a skeleton-spicules 
are sient and rather blunt amphioxi. More slender a 
amphioxi are occasionally found, but appear to be sasealy im- 
mature spicules. Spherical siliceous bodies have not been found. 
emmules.—No o gemmules have been foun 
Type-species (unique).—Potamolepis barroisi st, Topsent 
Distribution.—Only known from the Lake of Tiberias on 
the Jordan system in Palestin ne. 
The only other genus that approaches Cortispongilla in 
structure is Pachydictywm, Weltner, from which it is distin- 
guished chiefly by the formation of a regular skeletal cortex. 
The hardness of the sponge is due in a very large measure to 
this structure (pl. iv, figs. 3, 4). In the genus Veluspa, Miclu- 
cho-Maclay, which apparently occurs both in Lake Baikal (fresh 
water) and in Arctic Seas, a somewhat similar cortex is formed, 
but in an entirely different manner and not quite in the same 
position (pl. iv, fig. 5). 
Cortispongilla barroisi (Topsent). 
(Plate ii, figs. 1, la; plate iii, fig. 5; plate iv, fig. 4.) 
Potamolepis barroisi, Topsent, Rev. biol. Nord France, v, (1892). 
Weltner, Wiegm. Archiv. f. Naturgesch., Ixvii (1), p. 195 
(1901) 
My specimens of this species, which were taken in October, 
appear to be in a different phase of growth from those taken 
by Barrois in May, and also perhaps are somewhat better pre- 
served. It seems probable, to judge from Topsent’s figures, 
that, between these two months, the whole outer part of the 
I x 
amine ements of one of Topsent’s co-types. It is evident 
that this specimen was heavily parasitized by an alga and 
therefore sot probably more fragile than my own and some- 
external parts. There can, however, be no question as to the 
specific identity. 
