Vol. 55.] DEVONIAN EOCE-S OF NEW SOUTH WALES. 59 



plates shows the great number of forms possessing these characters, 

 but the proportion is even larger than the figures suggest, for the 

 forms without radial spines are comparatively rare, while the 

 spined forms are so abundant that in some thin sections no others 

 are recognizable. This remark, however, applies only to the dark 

 siliceous limestones which have had the calcite removed by acid; for 

 the radiolaria, in sections of the chert and of the claystones, appear 

 for the most part to be simple spherical or elliptical forms without 

 central tests and without radial spines. It is not at all probable 

 that such marked differences of character should occur in the forms 

 preserved in the cherts and claystones interstratified with the 

 siliceous limestones, and the apparent absence of the spines and 

 inner tests in the former beds may be attributed to the less perfect 

 condition of preservation of the radiolaria contained in them. 



As regards size, the Tamworth radiolaria appear to be relatively 

 small. The tests, in the large majority, range between 0*06 and 

 0-25 mm. in diameter ; exceptionally, larger forms occur : thus, for 

 example, in a section of black chert (No. 274 e) a simple oval form 

 measured 0*44 by 0-34 mm. 



The order Sphseroidea is the most numerously represented in the 

 Tamworth rocks ; somewhat more than half the species are included 

 in this division. With the exception of Trilonche^ gen. nov., the 

 species belong to genera previously recognized in Palaeozoic rocks. 

 With few exceptions these spheroidal radiolaria possess radial spines. 

 Three of the 4 genera of Prunoidea are new; they are charac- 

 terized mainly by the development of the radial spioes in connexion 

 with the ellipsoidal test. 



The 12 species of Discoidea belong to genera already known, but 

 5 out of the 8 genera of this division had not previously been re- 

 corded from Palaeozoic rocks. 



The only representatives of the subclass Nassellaria are spicular 

 bodies included in the order Plectoidea. These simple forms might 

 at first be mistaken for sponge-spicules, but neither in fossil nor in 

 recent sponges are spicules, similar in detail to these, known to 

 occur. 



As negative features of the Tamworth radiolarian fauna may be 

 mentioned the absence of the Discoidal genera LitJiocydia, Poro- 

 discus, AmphibracMum, and Rhopalastrum, common in nearly all 

 Mesozoic and Palaeozoic radiolarian deposits hitherto described, and 

 the yet more notable deficiency of any representative form of the 

 order Cyrtoidea. 



The corals in the limestones associated with the radiolarian rocks 

 at Tamworth (which have been determined by Mr. R. Etheridge, 

 jun.) indicate clearly the Devonian age of the latter. The only 

 rocks of this period containing radiolaria hitherto known are those 

 described by Dr. H. Piist from the Ural Mountains and from Hesse, 

 considered to be Lower Devonian in age, and from the Harz and 

 near Goslar, which are believed to be Upper Devonian.^ From these 



1 Palseontographica, vol. xxxviii (1892) pp. 113, 114, 122. 



