12 



tliat about five years ago, when examining tlie matrix of the 

 Trilobites from Arclrossan, with Dr. Henry Woodward, we 

 noticed fragments of an obscure fossil, believed to Ije those of a 

 coral, and evidently those referred to by Mr. Tepper, which 

 greatly puzzled us. They were described by Dr. Woodward in 

 the following words.* The calices " are about twelve millimetres 

 in diameter. The septa are numerous, and very short, with a 

 thickened spongy columella ; the corallites are irregular, and few 

 in number, and appear to be united by a cellular ccenenchyma." 

 The fragments referred to in this quotation I now know to be 

 the same as those at present under description. 



The genus Archoeocyathus, briefly stated, consists of free cup- 

 shaped or turbinate forms, with a tubular central cavity. " The 

 wall of the organism consists of an outer and inner lamina or 

 plate, bounding the exterior and the inner surface of the cup 

 respectively, and a series of stout A-ertical radial septa, which, 

 like those of a coral, extend from the outer to the inner wall 

 plates. Both walls are perforate, but a delicate imperforate en- 

 veloping lamina exists. The septa are also perforate, even in 

 thickness, and in their distance apart, the interseptal loculi being 

 tilled with dissepiments. The outer surface of the cup is either 

 smooth, horizontally ridged, or rugose. New septa are introduced 

 by intercalation. 



This is the general structure of ArcJueocyatJtus, Avithout enter- 

 ing into minute details, as emended by Dr. Hinde. The genus 

 EtltmopliyUinn is substantially the same, except that the inter 

 septal locali are not filled Avith dissepiments, and the inner wall 

 "instead of communicating with the interior of the cup or tube 

 by simple perforations consists of a series of relatively large 

 canals directed obliquely upward and inward, so that in trans- 

 verse section they present the appearance of one or more rows of 

 vesicles cut across." 



Archwocyathus is now known to occur in North America and 

 the island of Sardinia, and is characteristic of Lower Cambrian 

 strata ; whilst EtlimopliyUum has been met with in strata of the 

 same age in the country first named and Spain. 



The fossils from South Australia are either enclosed in lime- 

 stone or are on the weathered surfaces of the latter, with one or 

 two exceptions. They all present, more or less, the same appear- 

 ance, excepting only the colour of the limestone, Avhich varies 

 from dark bluish-grey to a light grey, or even a rock with a warm 

 reddish tint, as that from Ardrossan. The examples from Kanyka 

 are weathered partially out of the limestone, displaying the general 



* Notes on the Remains of Trilobites from South Aiistralia. Geol. Mag.^ 

 1884, iii., p. 342. 



