BY F. RATTE, ING. DBS ARTS ET MANUF., PARIS. 99 



or with such figures as I could compare it ; 1st, the external outline 

 of the moveable cheeks, and 2nd, the proportion that the length of 

 the pygidium bears to the length of the body, which proportion is 

 smaller than in any of the species brought into comparison with it. 

 It therefore remains to be named, or to be identified with some 

 species unknown to me. 



All the species mentioned above are placed by Barrande in his 

 " Etage E, Faune III," except A. Iloernesi, which belongs to his 

 " Etage, F, Faune, IV," and is found also in the next " Etage." 



On the same piece of rock with this minute Acidasjns is a hollow 

 impression of Stan7-ocephalus with which I shall deal hereafter. 



AciDASPis near A. Leonhardi, Barr. 

 Barrande, Syst. Sil. 1852, p. 720, PI. 37, fig. 1. 



(Plate II., figs. 2-4.) 



The remains of Acidaspis in the Bowning beds are rare indeed, 

 compared with with those of Encrinurus, Phacops, Sjihcerexochus, 

 Calymene, and Bronteus. (1) For the above reason, I will exhaust 

 the materials I have in hand and represent three more specimens, 

 two from Mr. Mitchell, and another given by him to the Museum. 



They all include the median part of the head only, and cannot 

 be properly identified, although the resemblance of one (fig. 4) to 

 A. Leonhradi is rather strong. The chief diflfei-ence is that in one of 

 them especially (fig. 3), the internal triangle of the fixed cheek of 



(1) The eai'liest mention that I know of the genus in Australia is by 

 Chas. Jenkins, Esq., of Yass, in Proc. Linn. Soc. Vol. III. pi. 17, where he 

 represents A. Biightii from the lower part of the Hume beds. I find ^4. 

 Brightii, Murch. from the Wenloch limestone, Dudley, figured in Murchison's 

 Siluria, pi. 18. However, from these data only it seems hardly possible to 

 ascertain this identification beyond doubt. [See also Barr. Sil, Syst. p. 752, 

 and in Phil, and Salter, Mem. Geol. Surv. Gt. Brit. 1848, Vol. 2, part I. 

 pi. IX). The pygidium of A. Brightii as represented by Mr. Jenkins, 

 somewhat resembles that i-epresented by me in Proc. Linn. Soc. Vol. I. 

 2 ser. pi. 15, fig. 12. (Subsequently I have been given to understand that 

 this gentleman did not intend to insist on the identification. ) 



