OF NEW SOUTH WALES. 



221 



In the pygydium especially, the smaller sized being longer in 

 proportion to the breadth, and semi-oval. 



In the larger (fig. 8), the outline forms a segment of a 

 circle described from the posterior angle of the furrow, separating 

 the axis from the pygydium. The anterior corners are slightly 

 rounded in the smaller but not in larger. 1 do not know, how- 

 ever, that theise variations are of specific value. 



Dimensions of Fig. 5 : — 



Whole length 60 millemetres 



Breadth of head segment .. ... 36 



Length „ 15 



Length of thorax .. ... ... 18 



Greatest breadth of axis ... ... 12 



Width of Pygydium ... 34 



Length,, „ 27 



Greatest width of Glabella .. ... .. ... 18 



Width at base 9 



Width between external edge of eyes ... ... 18 



Eeference to Plate 17. 



Fig, 1. — Homahnolus, from the lower division of the Hume beds (natural 

 size). 

 2. — Portion of head segment of Trilobite (twice the natural size) associ- 

 ated with Bronteus. 

 3. — Bronfeus, partly restored (natural size) \ 



4. — „ part of Glabella ,, I 



jj pygydium, largest found in these beds 



8. 



Hume beds 



6. — ,, portion of Thorax (twice the natural size) ; 

 7. — Cheireirus (natural size) lower part of Hume beds. 

 5.— Actduspis Brightii (natural size) lower part of Hume beds 

 9. — Phacops (natural size), Yass beds. 



Description of a new species of Vivipara. 



By J. Brazier, C.M.Z.S., Corr. Mem. Roy. Soc, Tas., &c., &c. 



Vivipara alisoni. 



Shell ovately conical, smooth, rather solid, white beneath a 



greenish-yellow epidermis, whorls 4i\ ; slightly convex, the last 



large, roundly convex ; umbilicus small, open, aperture pyri- 



formly ovate, peristome thin at the right margin ; base and 



