300 Dr. F. Briiggemann on Stony Corals. Fig. 2. Aphrocallistes Bocagei. Two nodes of the networlt, with two sex-radiate casts, each with one ray prolonged to form the interior of one of the long spines of the interior of the netted tube (Xl40). Fig. 3. Capitate termination of a spicular cast in the fibre of D. sub-glohosus (x435). Fig. 4. Farrea riensa. A node of the network, exhibiting casts of three imbedded spicules (xl04). Fig. 5. Hyalonema Sieholdii. Cut end of a length of the anchoring spicule, with the lamellar structure revealed by solution ( X 104). Figs. 6 to 9. Geodia arabica. Globo-stellates in various stages of solution : A, hilum ; r, radiate structure ; c, central cavity ; s, contained au--bubble (xl40). Figs. 10 & 11. Pacliymatisma Juhnstonia. Globo-stellates : p, hemispherical excavations ( x 140). Figs. 12 & lu. Geodia arabica. Spines of a globo-stellate separated by solution : tig. 12, seen in elevation ; fig. 13, in plan (x435). Fig. 14. P. Johnstonia. Globo-stellate : f, thin structureless external film of silica, separated from the rest of the spicule within it ( X 140). Fig. 15. Hemispherical excavations on the exterior of an acerate spicule of Geodia arabica : a, one showing the circular outcrop of the • concentric lamellae round its walls (xl40). Figs. 16 & 17. Ends of cylindrical spicules of Pachymatisma Johnstonia (X435). Fig. 18. Abnormal structure, showing two spicules of P. Johnstonia an-kylosed together ( X 140). Fig. 19. 2'rachya, sp. Acuate spicule : a, originally pointed end ; 6, rounded end (x435). XXXVII. — Notes on Stony Corals in the Collection of the British Museum. By Dr. F. Bruggemann. III. A Revision op the Recent Solitary Mussace^. Of the above-named group, which is equivalent to the Litho-phylliacees simples of Mihie-Eclwards and Haime, there appear to exist at least four genera comprising living species. They may be tabulated in the following manner : — A. Without a distinct epitheca 1. Scolymia. B. With an epitheca. a. Edges of the larger septa roughly lacero-dentate, the outermost teeth the strongest 2. Cynarina. h. Edges of the septa equally dentate. 1. Columella large, spongious 3. Antillia. 2. Columella small, trabecular 4. Homophyllia. Taking other characters into view, another arrangement can bsi made : —
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