BY R. ETHERIDGE, JUNR., AND JOHN MITCHELL. 705 



free cheeks, and in the structure of the pj'gidium, in which 

 characters it also differs from 0. Rattei, nobis. The tuberculation 

 is singular among the known Australian species. It resembles 

 0. Rattei in the proportionate length to width of the cephalon, 

 and in the pleurae being unispinate. 



In form it approaches 0. minuta, Barr., but as the late Mr. 

 Ratte pointed out, it bears only two rows of tubercles on the 

 pleural lobes, wliile on those of 0. minuta there are three rows; 

 and the largest of our specimens is not more than half the size of 

 that fossil. The genal and pleural spines are much larger in ours 

 than in the Bohemian species. 



Mr. Ratte seems also to have erred in fixing the number of 

 cheek spines at fourteen. We find them to be ten; and they 

 occupy two-thirds of the border, the anterior third being spineless. 



From 0. Dormitzeri our species differs in having a much more 

 quadrate cephalon, a highly granulose pygidium, and an absence 

 of the axial pleural spines. It is much nearer to 0. minuta, Barr., 

 and this is in all probability its nearest ally. The distinguishing- 

 features of 0. parvissima are — (1) The semicircular curve of the 

 borders of the free cheeks; (2) the fine acicular cheek spines; (3) 

 the subfalcate pleural spines ; (4) the tubercled pleural ridges ; 

 (5) the uniform tail spines, and absence of strong pleural ridges 

 (pads) on the pygidium; (6) the small central and lateral glabella 

 lobes; (7) the remarkably strong tuberculation of the whole test; 

 (8) its minuteness; and (9) the equality in the length of the thorax 

 and width of the head-shield. 



Our PL L., fig. 4, is drawn from the same specimen as Mr. 

 Ratte's t. 2, f. 1, bis. 



Loc. and Horizon. — Bowning Creek, Co. Harden, Lower 

 Trilobite Bed — Bowning Series (= I/iime Reds, Jenkins, and Yaas 

 Reds, David)-? Wenlock. Co//.— Mitchell. 



Odontopleura Jenkinsi, sp.nov. 

 (PL LiL, figs. 6-7; PL LiiL, figs. 4-7.) 



Acidaspis Rviyhtii, Jenkins (iion Murch,), Proc. Linn. Soc. N S, 

 Wales, 1879, iiL, p. 221, t. 17, f. 5. 



