706 SILURIAN TRILOBITES, 



Acidaspis Prevusti, Ratte [non Barr.), loc: cit. 1886, I. (2), Pt. 

 4, p. 1069, t. 15, f. 12 (excl.f. 11). 



JSp. Char. — This species is so near 0. Rattei, nobis, that it will 

 be sufficient for us to state the points of difference between the two 

 fossils on which we rely for justification in separating them. In 

 0. Jenkinsi the limb or margin in front of the glabella is smooth 

 instead of being dentated as in 0. liattei; each pleura of the 

 thorax bears two prominent tubercles, and some of the anterior 

 pairs four, the axis also appears more j^rominent. The pygidium 

 carries the same number of spines as that of 0. Rattei, but four 

 of them are constantly intermediate of the principal or axial pair. 

 The side lobes are more distinctly ridged and furrowed, the ridges 

 are surmounted by very distinct rows of tubercles. The pleural 

 ridges from the axial ring are less prominent than they are in 

 0. Rattei, but the tuberculation is more conspicuous throughout. 



Ohs. — We hesitated very much about according this foi'm 

 specific separation from 0. Rattei, and we do so only after 

 examining a great number of specimens and finding that the 

 characters already pointed out were constant, and because it comes 

 from a higher horizon and is not found associated with 0. Rattei 

 in the lower horizon, where that fossil is very numerous. 



We believe that this is the Acidaspid described and figured by 

 Mr. Jenkins as Acidasjns Rriyhtii,a.nd as pointed out by Mr. Ratte, 

 this appears to have been the first notice of the discovery of a 

 member of this family in Australia. AVith regard to its identifica- 

 tion with 0. (Acidaspis) Brightii, Murch., we are quite in accord 

 Avith the doubt expressed by Mr. Ratte, and also admitted by Mr. 

 Jenkins himself. The points which separate 0. Rattei from the 

 European and other members of the genus known to us, given 

 under its description, will also apply to this, except that it 

 approaches still nearer to 0. Leonltardi than does 0. liattei in 

 having a smooth frontal glabella margin. 



Loc. and Horizon. — Bowning Railway-Station Yard, Bowning 

 Village, Co. Harden, Upper Trilobite Bed — Bowning Series 

 { = Hume Beds, Jenkins, and Yass Beds, David) — ? Wenlock. 

 Co//.— Mitchell. 



