106 Frederick (Jhdpiixtn : 



proves that the internal surface of the pUite is exposed.^ The 

 hiteral, imbricating hinienae cross the plate from keel to margin 

 in a wide sigmoidal curve, excepting near the marginal border, 

 where they turn, with a sharp curve, towards the apex. Traces 

 of fine, interrupted, radial striae cross the lamellar surfaces. 

 This feature constitutes a distinctive character from that of 

 T. mitchtlli. 



Dimensions of Holotype. — Length, 5.75 mm. ; greatest 

 breadth, 3.83 mm. 



The second example of this species, here taken as a paratype, 

 may be a median plate since it is of exceptional breadth. It is, 

 however, of comparatively large size as compared with the 

 median plates of other species. The lamellar ornament is well 

 marked and the lateral upturned edges are seen to be distinctly 

 undulate, especially on the convex side of the fold. This plate 

 is exposed on the outer side, and the median fold is broad and 

 distinct. On the concave side of the median fold there is 

 another wide and shallow fold, which is feebly repeated on the 

 opposite side. The radial striae are more distinct in this 

 specimen, and are seen to extend over the area of the upturned 

 portion of the lamellae. 



Occurrence. — Type specimen from the grey mudstone of the 

 Yan Yean Reservoir tunnel, near Whittlesea ; coll. and pre- 

 sented by Mr. A. J. Shearsby, F.R.M.S. The ( ]) median plate, 

 from the mudstone of South Yarra ; coll. by Mr. F. P. Spry. 

 Silurian (Melbournian). 



Tuppilepas yeringiae, sp. ik.v. 

 (PI. XXVITI, Fig. 2). 



Description. — Remains of five covering plates with their 

 external surfaces exposed, arranged in a short conical group. 

 Two (?)me(lian plates rather shorter than the laterals, and not 

 quite so sharply folded in the median line ; in apposition. 

 Lateral or kite-shaped plates more elongate and acuminate ; 



1 For a description of tlie relationship of fold and keel, see F. R. C. Reed, " I'he 

 Structure of Turrilepas pcaelii and its Allies.' Trans. K. Soc. Fdin., vol. xlvi., i)t. iii.> 

 No. 21, 1908, p. 520. 



