70 



BRITISH FOSSIL SPONGES. 



skeletal-spicules of Cnemidiastrum Eoheneggeri, Zitt. (Fig. 4, c), from Upper Jurassic 

 strata at Cracow, and in species of Aulocopium, from Silurian strata in Gothland (Fig. 

 4, d). This latter genus has indeed been placed by Zittel in the Tetracladina family, 

 but in the character of its skeletal-spicules it appears to me more nearly to resemble 

 Cnemidiastrum than any tetracladine genus. Rarely, also, in some of the Sponges 

 of this family, spicules occur in which three subequal spinous rays radiate from a 

 common centre, thus approximating in form to the tetracladine spicules. Zittel 1 

 has figured a spicule of this form from Eyalotragos patella, Goldf. sp. 



xbo 







m 



Fig. 4. — Various forms of fossil lithistid spicules belonging to the families of the Rhizomorina, 

 Megamorina, and Anomocladina. (a) Branching, spinous, skeletal-spicule of rhizomorine lithistid, 

 Seliscothon Mantelli, Goldf. sp. (b) Two skeletal-spicules of the same Sponge, showing their 

 mode of union with each other, (c) Skeletal-spicule of the rhizomorine Sponge, Cnemidiastrum 

 Eoheneggeri, Zitt., from the Upper Jura of Cracow, (d) Skeletal-spicule of the rhizomorine 

 Sponge Aulocopium, sp. from the Silurian of Gothland, {e) Skeletal-spicule of a megamorine 

 Sponge, Doryderma, sp. from the Senonian strata of Coesfeld, Westphalia. (/) Skeletal-spicules 

 of Doryderma, showing their mode of union with each other, (g) Skeletal-spicule of the mega- 

 morine Sponge, Carterella, sp. (h) Portion of the skeletal mesh of the Anomocladina Sponge, 

 Astylospongia, sp. from the Silurian of Gothland, showing the spicules and their mode of union 

 with each other. 



(b) Megamorina — The skeletal-spicules of this family consist of a straight, or, 

 more frequently, variously curved, elongated main axis, which may either be 

 simple, or may give off irregular branches in different directions (Fig. 4,e,f,g). 

 The terminal ends of the main axis and of the branches either form tapering 

 blunted processes, or more usually expand into flat or concave, spoon-shaped 

 surfaces. Both the tapering extensions and the concave expansions may be 



1 ' Studien ueber fossile Spongien,' ii, Taf . 3, fig. 4. 



