78 RECORDS OF THE AUSTRALIAN MUSEUM. 



HALYSITES IN NEW SOUTH WALES. 



By R. Etheridge, Junr., Curator. 

 (Plate xvii.) 



The history of this genus, not only in N. S. Wales, but in 

 Australia generally, is a very brief one. Halysites was first 

 recorded by the late Prof. L G. de Koninck,* who recognised 

 //. escliaroides, Lamk., in the collection of N. S. Wales fossils sent 

 him by the late Rev. W. B. Clarke for determination. In the 

 description given, however, there are no characters that would 

 readily differentiate between this species, and the typical H. 

 catenulatus, Linn. De Koninck gives Wellington as the locality, 

 but I have never seen a Halysites from the limestone of that 

 district. 



Although the presence of this old Palpeontological landmark 

 has been in a generic sense, recorded as occurring in N. S. Wales, 

 the microscopic structure has not been investigated, so far as I 

 know. 



The largest fasciculo-reticulate corallum that has come under 

 my notice is a specimen measuring six and a half inches by 

 four and a half, forming, in every case, a lax and spreading mass 

 rather than a high erect growth. The intersecting reticulations, 

 or " fenestrules," are very variable in size and shape, but always 

 polygonal, the smaller having an average size of three by three 

 mm., the largest observed fifteen by five mm., fourteen by twelve, 

 and so on, with intermediate gradations, the angles of junction of 

 the vertical lamina? or plates being equally variable. The reticu- 

 lations are usually longer in one direction than another, but not 

 by any means invariably so. The walls are strong, but in conse- 

 quence of the alteration that has taken place, the epitheca on the 

 free sides of the lauiinje is rarely discernible, but when so, is well 

 developed. The number of corallites on any one side of a reticu- 

 lation varies from two to twelve, but the average number is from 

 four to six. 



Examination in thin sections renders the great amount of alter- 

 ation the corallum has undergone apparent, an unfortunate cir- 

 cumstance common to a large number of our Lower Palaeozoic 



* Foss. Pal. Nouv.-Galles du Sud, pt. 1, 1876, p. 16 ; Clarke, Sed. Form- 

 ations X. S. Wales, -Ith Edit., 1878, p. 129. 



