237 



place at the base of the sponge, and in another near the 

 periphery. The walls of the larger cavities branched in a 

 dichotomous manner. The smallest cavities were i cm. in 

 diameter, and the largest 5 x 2.5 cm. in size. The average 

 thickness of the partition walls was about 3 mm., but in one 

 place the cortex attained a thickness of 1.5 cm. The distinctive 

 features of the species are the labyrinthine skeleton, the 

 presence of chiasters, and absence of spirasters. 



The other species of this genus (P. carinata Bowerbank ; P. 

 melobesioides Gray ; P. intermedia Sollas ; P. decoiiicans 

 Hanitsch ; P. mixta Thiele) all possess well-marked tyles. 



The presence of chiasters is so exceptional that I thought at 

 first that I had to deal with a Geodine sponge, but there were 

 no triaenes to be found. 



Genus Latrunculia (Bocage). 



Latrunculia natalensis, sp. n. 



Plate v., Fig. 2. Plate VI., Fig. 2a-e. 



Sponge small, with long slender stalk and pyriform head 

 with an oscule at the summit surrounded by a fringe of 

 spicules. Surface (when viewed through a lens) slightly 

 hirsute. Colour sandy. Skeleton formed of an axial stalk 

 projecting about half way into the body, and of spicule bundles 

 radiating out from a point below the centre ; ectosome formed 

 of a thick crust of sterrasters. Discasters of two kinds, somal 

 and choanosomal. 



Spicules. Megascleres. — Styles (rare) 700x10/", smooth, 

 slightly curved. 



Strongyle 500 x 23 /*, slightly curved near the centre. 



Amphioxea or tornote in bundles and forming the oscular 

 fringe) 540 x 10 /^, frequently pointed abruptly at one end 

 and gradually at the other. 



Microscleres. — Somal discaster, total length and breadth 

 36 x 23 M ; with a basal verticil of four simple spines, two 

 large central oppositely directed verticils of compound spines, 

 and a small verticil of simple spines appressed to the apical 

 spine. 



Choanosomal discaster with simple spines, 86 /« long, with 

 two oppositely directed verticils each composed of four simple 

 spines 21 /^ long. 



Locality E. — Cone Point, Natal, 34 fms. ; growing attached 

 to Tetlixa })iagiia. 



The one specimen is 19 mm. in length, the head being 4*5 

 mm. in length by 2 mm. in breadth. 



