172 THE SILURIAN TRILOBITES OF NEW SOUTH AVALES, 



We have not noticed any trace of fimbriate pygidia in any 

 Australian Gyjihasins. 



Log. and Horizon. — Downing, Co. Harden — Upper and Middle 

 Trilobite beds; Limestone Creek, near Bowning, Co. Harden — 

 Middle Trilobite bed, Bowning Series (? Wenlock) (Coll. Mit- 

 chell). 



The majority of the specimens figured are from the Upper Trilo- 

 bite bed, but many cephalic-shields, two of which are figured, were 

 obtained from the Middle Trilobite bed (PI. vi. fig. 3/i, 3j). The 

 latter we are not able to separate from those of the former ; and 

 therefore, like Froetus howningensis and Acidaspis longispinis, 

 this species was one of the most persistent Trilobites of that 

 geological age. 



Cyphaspis yassexsis, sp.7iov. (PL VI. figs. 1, \a-d). 



Sp. Char. — Entire body unknown. Cephalic-shield semicircular, 

 with a wide somew^iat concave limb, the edge reflected upwards 

 and thickened; glabella pyriform, arched in the middle line, 

 narrowing rapidly towards the posterior, with a wide anterior 

 border, axial furrows very marked towards the front, less so in 

 the middle of their course and behind ; first pair of glabellar 

 furrows somewhat indicated by a slight lateral compression on 

 each side of the glabella ; circumscribed lobes small, oval ; facial 

 sutures anterior to the eyes gently directed outwards, curving 

 inw^ards along the limb and cutting it nearly in lines opposite 

 the original point of departure from the eyes, posterior to the eyes 

 very short, cutting the hinder margin of the cephalic-shield close to 

 the glabella ; neck furrow moderately distinct, depressed on each 

 side; fixed cheeks small; eyes large, reniform, and faceted; eye 

 lobes moderately large, semicircular; free cheeks large, very tumid 

 towards the eyes ; genal angles produced into comparatively large 

 and gently incurved spines, their limbs striated ; supposed audi- 

 tory organs situated between the front margin of the glabella and 

 the facial sutures. Thorax only known by disjointed segments, 

 but with a very prominent axis ; pleurae distinctly furrowed, the 



