a 
PORIFERA OF THE L.M.B.C. DISTRICT. 935 
but their fourth ray, which stands vertically upon the 
three others, is short and hook-hke. It measures 0°03 
mm. In addition to these spicules we find large gastral 
tetract spicules. They consist of three short rays (0:14 
mm.) which le in one plane, and of a fourth long ray 
(0°43 mm.), which stands at right angles to the former. 
The short rays are shghtly curved, they he in the inner 
surface of the body-wall and parallel to its circumference. 
The fourth ray projects freely into the gastral cavity. These 
tetract spicules are very numerous, so that their short rays 
form a kind of dense basket-work on the inner surface of 
the body-wall. 
The spherical flagellated chambers of this species and its 
ramifying canals place it amongst the Leuconide, and its 
triact and tetract spicules bring it under the genus Leu- 
caltis, Heckel. Following now Heckel’s ‘“‘ Ubersicht der 
6 Species des Genus Leucaltis,’* and taking no notice of 
the tetracts with the one hook-lke ray, we arrive at Leu- 
caltis pumila, Bowerbank. 'The respective steps in that 
“ Ubersicht”’ are: 1. ‘“‘Skelet nicht scharf getrennt in 
ein vollig verschiedenes Rinden-und Mark-Skelet.” 2. 
“Hauptmasse des Skelets aus Dreistrahlern gebildet.’ 
3. ‘‘ Vierstrahler entweder bloss in der dermalen oder 
bloss in der gastralen Flaiche. Alle oder ein Theil der 
Dreistrahler und Vierstrahler nicht regular.” 4. ‘“ Vier- 
strahler bloss in der stacheligen gastralen und canalen 
Flache.” 5. ‘‘ Basal Strahl der Vierstrahler linger als 
> 
die lateralen.—Leucaltis pumila.” Yet when we compare 
the specific characters of Leucaltis pumila, as given in the © 
detailed descriptions of Heckel and Bowerbank,+ with our 
species, we find so many and such great differences between 
these two forms that I feel obliged to establish a new 
* Heckel, ‘‘ Die Kalkschweemme,” Bd. ii.. p. 143. 
+ Bowerbank, “ British Spongiadee,” vol. i1., p. 41, 
