M. K. A. Zittel on Fossil Lithistidte. 235 



'XXNW.— Studies on Fossil Sponges. — II. Lithistida^. 

 By Karl Alfred Zittel. 



[Contimied from p. 1.35.] 

 AttemjJt at a Classr/ication of the Lithistidce. 



As to the position of the Lithistidse with respect to the 

 other sponges, the opinions of zoologists are somewhat 

 divergent. 



O. Schmidt*, in his last great memoir, groups all sponges 

 in foar orders : the first contains the Hexactinellidse with sex- 

 radiate spicules ; the second includes the sponges with anchor- 

 shaped spicules, or with spicules of the pyramidal type ; the 

 third those with uniaxial siliceous spicules and all forms desti- 

 tute of spicules ; and the fourth the Calcispongise. 



In the second order we find the family Lithistidaj, together 

 with the Geodinidas, the Ancorinida3, and the fossil Vermicu- 

 latge. That this last family (which, however, is only provi- 

 sionally established) cannot be maintained, as it consists of 

 the most discordant elements, I have already demonstrated 

 elsewhere f. Consequently there remain for the second order 

 only the former Corticata3 (Geodinidce and Ancorinidte) and 

 the Lithistidse. 



We find the Lithistidte in a similar position in the third 

 edition of Claus's '■ Handbuch der Zoologie.' Claus places 

 the Calcispongiffi, as an equivalent group, opposite to all the 

 other marine sponges (Fibrospongia). The Fibrospongia are 

 divided into twelve families, closed by the Ancorinidas, Geo- 

 dinidfe, Lithistidaj, and Hexactinellidse in the sequence stated. 

 Here, therefore, we also find the Lithistidte in the immediate 

 neighbourhood of the Geodinidee and Ancorinidte on the one 

 hand, and of the Hexactinellidaj on the other. 



A different and somewhat more complicated arrangement of 

 the sponges has been proposed by H. Carter |. Of Carter's 

 eight orders, Carnosa, Ceratina, Psammonemata, Rhaphidone- 

 mata, Echinonemata, Holorhaphidota, Hexactinellida, and 

 Calcarea, the first five and a great part of the sixth correspond 

 to Oscar Schmidt's third group. Each of the first five orders 

 is subdivided into from two to four families, and these again 

 into a great number of groups. 



The order Holorhaphidota is the most comprehensive of all, 

 and is formed of constituents whicli ought hardly to be placed 



* Grundziige einer Spongienfaiina des Atl. Geb. p. 83. 

 t Studien iiber fo.-jsile Spongien, i. p. G ; see Ann. & Mag. Nat. Illst. 

 sev. 4, vol. XX. p. 200. 



[ Ann. X: Mag. Nat. Hist. ser. 4, vol. xvi. (187")) }ip. 1, liH, 177. 



IG* 



