488 EICHARD EVANS. 



PLATE 38. 



Fig. 6. — (x 200.) The skeleton near the surface as seen in section. 

 Tlie spongiu is shown forming a thin layer at the surface and covering the 

 fibres in the interior. 



Fig. 7. — (X 800.) A portion of two fibres with a large connecting 

 spicule and a much finer one with a swelling. The spongiu is greatly thickened 

 at the points where the connecting spicules enter the main fibres. 



Fig. 8. — (X 45.) The skeleton as seen in a section passing from the 

 base to the upper surface. A portion of the shell on which the sponge was 

 growing is seen at the bottom of the figure. 



Fig. 9. — (X 200). A portion of the skeleton of Spongilla tan- 

 ganyikse seen in section near the surface, showing the main fibres formed 

 almost entirely of spiny spicules, while both spiny and smooth ones are found 

 scattered about irregularly. 



Fig. 10. — (X 400.) Spicules of Spongilla tanganyikse. a—f. 

 Straight spiny amphistrongyla. _^audj. Straight, spiny amphitornota. h^ 

 k, and/. Straight, sparsely spined amphioxea. o, p, and 5'. Straight, smooth 

 amphioxea. m. Irregularly shaped, spiny spicule, n. Microsclere. 



Fig. 11. — Potamolepis spicules from the mud of Lake Tanganyika, a and 

 b. Two large spicules with a curved shaft and swollen ends, i.e. curved 

 amphitylota. c, d, and e. Three intermediate spicules with curved shaft and 

 rounded ends, but not swollen, i. e. curved amphistrongyla. ./ and ff. Two 

 small spicules similar to c, d, and e, i. e. amphistrongyla. 



