A VKKY KKMAHKAJiLK SJ'KCIES OF 



SPONGOrHYLIJM FROM THE UPPKFl SILURIAN 



ROCKS OF NEW SOUTH WALKS. 



B}- II. Fi'1IKi;iim;k, .Itm;., Cm-atoi'. 



(i'lates iv-vii.) 



^riie .subject ot the present papei' tirst caiiie under my iiDtice 

 whilst engaged in a ge()h)gical travei-se of tlie Ujiper Silurian 

 beds exposed in the coui-se of the Yass River, between the 

 town of the same name and the Devil's Punch-bowl, )iear tlie 

 Yass-Murrumbidgee Rivers Junction. The specimens so 

 obtained wei*e subsequentlv augmented by additions made by 

 Mr. A. J. Shearsby. 



Genus Spongoj)liyllum, Kihrmils uinl llniuK, 1851 ^ 



(Polyp. Foss. Terr. Pal., I80I, p. 425.) 



Sp()ngo])hyllum enorme, .-7/. nor. 



(Plates iv-vii.) 



Sp. ('It((rs. — Coralluni compound, in the form of very large 

 spreading masses with an uneven or undulating upj)er surface. 

 Cm-allites very large, separating from one another on percussion, 

 polygonal (quadrangular, pentagonal, or hexagonal), defined 

 at the surface by grooves, and formed by a sei-ies of close- 

 titting invaginated cups, sometimes two and a half inches in 

 diameter. Theca ill developed and often undefined. Calices 

 funnel-shaped, moderately deep, flat bottomed, to some extent 

 flattened around the peripheries, thence shelving inwards and 

 downwards, average diameter one half to three quarters of an 

 inch. Visceral chambei-s simply defined by the edges of 

 inturned vesicular ])lates, and by successive repetition forming 

 the general mass of each corallite. Septa numerous but weak, 

 visible only as short lamiiife around the edges of each calicular 

 fossa passing for a brief distance on to the central, flat, tabulate 

 area, and sometimes faintly continued over the funnel-shaped 

 peripheral surfaces of the calices. Tabula? incomplete, con- 

 sisting of flat or slightly rolling close plates forming lenticular 

 vesicles which pass insensibly into the general body of smaller 

 vesicles forming the peripheral mass of each corallite. 



' Emended Schliitcr. 



