108 Frederick Cha'priian : 



wards to meet the gently sinuous ventral margin at a moderately 

 wide angle ; dorsal border widely curved and sloping rapidly 

 towards the back to meet the short posterior margin ; the latter 

 nearly straight or slightly concave, and sharply angled above 

 and below. 



Description of Young Forms. — These are more regularly 

 ovoid, with stronger dorsal and ventral curvatures, and absence 

 of angulation at the extremities. One of the examples shows 

 the existence of a moderately broad ventral flange. 



Dimensions of Holotype. — Length of carapace, 23.5 mm. ; 

 greatest height, 13 mm. ; length of exposed abdominal series of 

 segments, 11 mm. Average length of abdominal segments, 

 cir. 3 mm. 



Silurian (Melbournian). South Yarra ; in mudstone. Found 

 by Mr. P. Taverner. 



Affinities. — This is a peculiar form of the genus on account of 

 the inflated appearance of the carapace, and the highly curved 

 dorsal line. There seems to be no very closely related form to 

 this, the nearest being Ceratiocaris cassioides, T. R. Jones and 

 H. Woodward,^ a species found in the Lower Ludlow of Leint- 

 wardine, Shropshire, associated with small brachiopods and 

 Cardiola cornucopiae. 



Remarks. — Examples of the present species are very numerous 

 in the grey and brown mudstone of South Yarra (Yarra Im- 

 provement Works), but are nearly all indifferently preserved. 

 It was apparently gregarious in habit, since one slab of mud- 

 stone showed traces of nearly a score of individuals crowded 

 together. The general appearance of the specimens is that of a 

 swollen subovate carapace-cast, which is almost invariably 

 stained with carbonaceous material. In the type-specimen 

 there is a circular elevation of the matrix on the upper anterior 

 area of the carapace, suggestive of an ocular spot ; but since 

 several of the earlier described so-called ocular-bearing phyllo- 

 carids, owing to illusionary cavities and fragments of matrix, 

 have now turned out to be really referable to Ceratiocaris, it 

 necessitates great care in their interpretation. Should an 



1 Mon. Brit. Palaeozoic Phyllopoda, Pal. Soc, 188S, p. 59, pi. iii., fij^-. 9 ; pi. iv., fig. 7 

 pi. vii., figs. 4-6. 



