456 



ON AFRICAN CALCAREOUS SPONGES. [May 12,: 



The triracliates are of two sorts : — 



(b) Alate triracliates from the dermis. Basal rays straight, 

 150-240 /x long X 10-13 /x thick. Paired rays, curving slightly 

 upwards, 160-320 /^ long x 9-13 ja thick. Oral angle 110°. 



(c) Subregular triradiates from the body. Rays very sharply 

 pointed, 600-950 fx long x 35-40 /x thick. Individual spicules 

 often have their three rays of different lengths, but the angles 

 are always approximately 120°. 



The quadriradiates are of three sorts : — 



(d) Subdermal quadriradiates. These spicules vary enormously 

 in size, and are of peculiar form as shown in the drawing. The 

 facial rays are folded inwards, i. e. towards the_ side from which 

 the apical ray projects. The maximum facial ray found is 

 700 fj. long X 26 /A thick. The maximum apical ray is 500 /x long 

 X 26 [x thick. 



(e) Alate quadriradiates from the lining of the excurrent canals. 

 Basal rays straight, 280-480 /x long x 20-28 fi thick. Paired rays 

 nearly straight, 340-420 yio long x 14-24 /x thick. Oral angle 

 130°. 



(/) Alate quadriradiates from the gastral layer. Basal rays 

 straight, 300-560 fi long x 10-12 /x thick. Paired rays, bending 

 upwards, slightly irregularly bent, 240-450 /x long x 8-10 /x thick. 

 Apical ray, curved orally, 180-260 /x long X 8 /x thick. Oral 

 angle 110° to 120°. 



List of Literattire referred to in the paper. . ' 



(1) Haeckel. — Die Kalkschwamme. Berlin, 1872. 



(2) PoLEjAEFF. — Challenger Report, Monogr. viii., 1883. 



(3) Dendy, a. — " Studies on the Comparative Ana,tomy of 



Sponges. Y. Observations on the Structure and Classifi- 

 cation of the Calcarea Heterocoela." Q. J. M. S. vol, xxxv, 

 (1893) pp. 159-257, pis. x.-xiv. 



(4) MiNCHiN, E. A. — A Treatise on Zoology. Edited by E. Ray 



Lankester. Part II. The Porifera and Ccelenterata. 

 Chap. 111. S2ionges, by E. A. Minchin, M.A., 1900. 



(5) Minchin, E. A. — "The Characters and Syponymy of the 



British Species of Sponges of the Genus Leucosolenia." 

 Proc. Zool. Soc. Lond. 1904, vol. ii. pp. 349-396. 



(6) Minchin, E. A. — " On the Sponge Leucosolenia cortorta 



Bowerbank, Ascandra contorta H., and Ascetta spinosa 

 von Lendenfeld." Proc. Zool. Soc. Lond. 1905, vol. ii. 

 pp. 3-20. 



(7) Lenbenfeld, R. von. — "Die Spongien der Adria : I. Die 



Kalkschwamme." Zeitsch. wiss. Zool., liii. Bd., 2 u, 3 

 Heft., 1891. 



