OF NEW SOUTH WALES. 27 



wit,h a large Trilobite closely allied if not identical with Phacops 

 longi caudatus which occurs in the top beds. One Galymene is 

 undoubtedly Galymene duplicata. The Spherexochus is almost 

 identical with Spherexochus mirus as figured by Murchison. 



Size of largest Galymene 2J inches in length. 



Size of largest Spherexochus 2 inches in length. 



The Trilobite in the upper bed (PI. YI, fig. 1), which is an 

 impure limestone, is chiefly associated with a Petraia Some parts 

 of this limestone literally swarra with segments of this Trilobite. 

 I have, however, obtained one cast, rather mutilated, of the whole 

 body, and another whole Trilobite doubled up. The head segment 

 of this Trilobite is very like that of Dalmania pleuroptyx as figured 

 by Dana, both in its general proportions and the direction of the 

 facial suture ; the furrows on the Griabella are straighter in Dana's 

 figure than on any specimen I have. D. pleuroptyx is a Silurian 

 species, though, like Phacops, Dalmania is both a Devonian and 

 Silurian genus. 



These Trilobites attained a size of 5 inches in length exclusive 

 of the spinose caudal appendage. 



As I have obtained no fossils in the next division and as after 

 attaining a thickness altogether of 2,000 feet these beds by 

 folds and fauUs repeat themselves until they reach the Igneous 

 Rocks, I shall not at present trace them farther. 



In comparing the results obtained from the Yass and Hume 

 beds, I think that there is sufficient evidence in the similarity of the 

 fossils to shew that they must both be classed in one formation. 



I cannot speak of the exact number common to both, but there 

 are certainly among the Brachiopods — two species of Atrypa, 

 including Atrypa reticularis — several of the genus Spirifera, 

 including two plaited Spirifers, two of Strophomena, and one 

 of Betzia. Of Couchifers I believe several, including an Orthon- 

 otus and a Pterinea ; a Murchisonia among the Gasteropods ; 

 of the Trilobites Bronteus and Gromus. There is no doubt 

 about the Gromus ; the Bronteus is, however, in the Yass beds so 

 small, and the markings so indistinct, that it is not possible to 

 speak with certainty, but what can be seen makes it probable that 

 it is identical with that found in the Hume beds. 



