PORIFERA OF THE L.M.B.C. DISTRICT. 235 



but their fourth ray, which stands vertically upon the 

 three others, is short and hook-like. 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 lie in one plane, and of a fourth long ray 

 (0'43 mm.), w^hich stands at right angles to the former. 

 The short rays are slightly curved, they lie 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 aud its 

 ramifying canals place it amongst the Leuconidae, and its 

 triact and tetract spicules bring it under the genus Leu- 

 calt'is, Haeckel. Following now Haeckel's " Ubersicht der 

 6 Species des Genus Leucaltis,"* and taking no notice of 

 the tetracts w4th the one hook-like ray, we arrive at Leu- 

 calt'is pumila, Bow^erbank. The respective steps in that 

 "Ubersicht" are: 1. " Skelet nicht scharf getrennt in 

 ein vollig verschiedenes Kinden-und Mark-Skelet." 2. 

 " Haupt masse des Skelets aus Dreistrahlern gebildet.' 

 3. " Vierstrahler entweder bloss in der dermalen oder 

 bloss in der gastralen Flache. 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 langer als 

 die lateral en. — Lexical tis pumila.'' Yet when we compare 

 the specific characters of LeucaltU pumila, as given in the 

 detailed descriptions of Haeckel and Bowerbank,t with our 

 species, we find so many and such great differences between 

 these two forms that I feel obliged to establish a new 



* Hreckel, "Die Kalkscliwaemme," Bd. ii, p. 143. 

 t Bowerbank, "British Spongiad.T," vol. ii., p. 41. 



