869 



ON A NEW SPECIES OF RHIZOFHYLLVM, FROM 

 THE UPPER SJlLURIAN ROCKS OF YASS, N.S.W. 



By a. J, Shearsby. 

 (Communicated by Fred. Turner, F.L.S., dec.) 



(Plate xxvi.^) 



Rhizophyllum yassense, sp.nov. 



The well-known Silurian deposits of the Yass district have 

 been responsible for many forms of fossils new to science; and 

 although the district has been under observation for many years, 

 it is far from being overworked, and would well repay a more 

 detailed geological inspection than it has hitherto received. 

 Among the most interesting corals to be found in this district are 

 the Calceola-like operculate rugose corals, Rhizophyllum inter- 

 pu7ictatum, De Kon., and B. australe, Eth. fil. Both of these 

 forms have been fully described by Mr. R. Etheridge, Junr., in 

 the " Records of the Australian Museum " (Vol. 1, No. 10, Dec, 

 1891). I have now to record another form of Rhizo2)hyllum 

 which I found in Derrengullen Creek between Yass and Bowning, 

 which differs in so many respects from the above-mentioned forms, 

 that I feel justified in referring it to a new species. 

 The following is a description of this new form : — 

 Corallum simple, pyramidal, short, widely expanded above, 

 obtusely pointed below, lateral angles rounded and obtuse, section 

 suboval plano-convex; dorsal surface convex; ventral surface flat 

 transversely, but longitudinally the lower two-thirds are flat, 

 and the upper one-third curved inwards towards the calice. 

 Calice of a distinct crescentic shape, deep, extending to a depth 

 of about one-half the height of the corallum, and possessing a 

 well-marked subcentral depression ; dorsal margin sharp and 



* The Plate lettered PI. xxvii. should have been PI. xxvi. 



