ASTYLOSPONGIA. 91 



Order HEXACTINELLID^, Oscar Schmidt. 

 Suborder DICTYONINA, Zittel 

 Family ASTYLOSPONGID^. 



Genus ASTYLOSPONGIA, Ferd. Ecemer, 1860. 



Ferd. Roemer described the minute structure of A. prcBinorsa, the typical species 

 of the genus, as consisting of very regular six-rayed, star-shaped bodies, which are 

 connected together by the intermediate union of the rays of each body with the rays 

 of those immediately adjoining ('Die silur. Faun, des west. Tenn.' p. 8). In a 

 later definition of the genus (' Lethea Palseozoica,' 1 Th. p. 307) the same author 

 states that the skeleton consists of a net-like web, composed of nodes, from which 

 six rays extend at right angles with each other, and unite with the rays of the 

 adjoining nodes. Prof. Zittel (' Studien,' 1 Th. p. 45) states, in his diagnosis of the 

 genus, that the skeleton consists of amalgamated six-rayed spicules with solid nodes, 

 forming an irregular net-work with triangular, quadrangular, or polyangular meshes, 

 and that, as a rule, the arms of several adjoining spicules attach themselves to a 

 single node. In 1878 Dr. K. Martin published a very important memoir on the 

 structure oi Astylospongia ('Archiv des Vereins der Freunde der Naturgeschichte in 

 Mecklenburg '), in which he states that the number of the rays which radiate from a 

 single node vary from six to nine in number, and that they radiate in most variable 

 directions in order to unite with other rays to form a new node. He also made the 

 interesting discovery that the terminations of the rays divide into minute branches 

 {loc. cit. Taf. 1. f. 3). These facts led Dr. Martin to express the opinion that there 

 were wide difiierences between Astylosjjongia and typical Hexactinellids. In a short 

 comment on Dr. Martin's memoir, Prof. Zittel ('Neues Jahrbuch,' 1877, p. 709) 

 states that the branching of the termination of the rays is entirely the result of the 

 state of preservation of the specimen, and that in unaltered examples the nodes are 

 always solid. 



An examination of the microscopic structure of Astylospongia prcemorsa from 

 Tennessee leads me to confirm the observations of Martin that the spicules of this 

 species are composed of solid nodes with from six to nine smooth arms which radiate 

 from the centre in diff"erent directions and at varying angles. The terminations of the 

 arms or rays of adjoining nodes unite together, and appear to form nodes by their union, 

 which, when the specimen is unaltered, cannot be distinguished from the nodes from 

 which the arms themselves originated ; but in specimens where a certain amount of 

 alteration has taken place, these secondary nodes can be seen to be composed of the 

 expanded terminations of the arms of several spicules united together. If this view 



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