imperfectly -knoivn Species of Stroviatojwroidti. 229 



average distance separating the concentric lamina. The hori- 

 zontal " arms " given out by the radial pillars are regularly 

 produced in whorls and give rise to an angular meshwork. 



Obs. This species was identified by Bargatzky with the 

 Stromatopor-a ostroites of von Rosen. I have, however, 

 carefully examined the original specimens of von Rosen's 

 species and find it to be quite distinct, as I shall immediately 

 show. It has therefore been necessary to give a new specific 

 name to the present species. A. hehhornense is nearly related 

 to A. clathratum, but differs in the obvious character of the 

 possession of numerous large astrorhizEe, which, according to 

 my observations, are usually arranged in vertical groups and 

 are connected with a main vertical canal belonging to each 

 group. From the presence of the astroBliizaj the species 

 resembles the form which I shall describe as A. stellulatumj 

 with which I was at first disposed to identify it (Mon, Brit. 

 Strom, p. 76). Further examination, however, has shown 

 tliat it is only in this single character that these two forms 

 are closely related. The nearest ally of A. hehhornense is 

 undoubtedly A. clathratum^ the two agreeing closely in 

 general structure, and especially in the fact that the " arms " 

 in both give rise to a regularly angular network (PL VII. 

 fig. 7). The species is, however, distinguished from A. 

 ckithratum not only by its abundant and large astrorhizse, but 

 also by the much more slender and delicate character of the 

 radial pillars (PI. VII. fig. 8). 



Formation and Locality. Abundant in the Middle Devonian 

 of Hebborn (Schladethal), in the PafFrath district. I have 

 not yet identified this species from either the Eifel or from 

 Devonshire. 



Actinostroma? astroites^ Rosen. 

 (PL VI. figs. 6-7 a.) 



Stromatopora astroites, Rosen, Ueter die Natur der Stromatoporen, 



p. 6'2, pi. ii. tigs. (J and 7 (18Q7). 

 [!Non iStromatopura astroites, Bargatzky.] 



The coenosteum of this species is massive and grows in suc- 

 cessive strata, or " latilaminee," of varying thickness. The 

 surfaces of all the strata are covered with well-marked 

 branching astrorhizse, the centres of which are placed about 

 10 or 12 millim. apart. In minute structure the skeleton is 

 apparently formed of exceedingly delicate and close-set radial 

 pillars, which are placed from yV to jV miilim. apart or 

 even closer, and are united by few horizontal " arms." Tan- 

 gential sections hence show a very delicate " hexactiuellid " 



