(00 



NOTE ON A NEW SPECIES OF FAVOSITES FROM 

 YASS DISTRICT, N.S.W. 



* 



By a. B. Walkom, B.Sc, Demonstrator in Geology,. The 

 University of Sydney. 



(Plates xxx.-xxxi.). 



Favosites tripora, sp.nov. 



Specific Characters. — Corallum compound, massive. Coral- 

 lite-tubes prismatic and polygonal-quadrangular to hepta- 

 gonal, but with pentagonal and hexagonal greatly predomi- 

 nating, and all of approximately uniform size. The average 

 diameter of the corallite tubes is 2^-3 mm. The walls are 

 slightly thickened by deposit of secondary material ; the pri- 

 mordial wall is very thin. No longitudinal striae are visible 

 on the walls. The mural pores are of medium size, and have 

 no elevated rim surrounding them. There are usually three 

 rows, sometimes two, alternately placed and about the same 

 vertical distance apart as the tabulae. Septa are well-developed 

 short spines, 12 in number, regularly placed, and reaching 

 only a short distance in from the wall. They are most fre- 

 quently ranged on the walls of the corallites, and only 

 occasionally occupy the angles. Tabulae are numerous and 

 complete, almost straight, and often markedly bent down- 

 wards near the walls; occasionally they branch. They are 

 not thickened by secondary material. They are fairly close 

 together, averaging about two to the millimetre ; they are 

 usually opposite one another, or nearly so, in adjacent coral- 

 lites. Old chambers are transversely oblong, with a length of 

 about twice and one-half the height. 



