185 



striated ; hinge usually very elongate, broadly excavated in the 

 middle. 



Locality. — Common in ths upper beds at Muddy Creek (J". 

 Dennant /) 



This new species has considerable affinities with O. undata 

 Larnk., of the Tertiary beds of Europe, but has a narrower and 

 •deeper lower valve, which is devoid of radial plications ; it is 

 ulso something like the recent O. Virginica of the same author. 

 It is very different from any known species inhabiting the Aus- 

 tralian seas. 



Pecten deformis, spec. nov. Plate xviii., fig. 4. 



Triangularly ovate, compressed, obliquely extended pos- 

 teriorly and inequilateral; in the young state regular, sub- 

 equilateral. 



The young regular stage of growth is seen for about 30 

 millimetres from the umbo ; is ornamented with about 50 radial 

 subacute narrow ribs, usually grouped in threes, the middle one 

 being the larger, and with quincuncially arranged depressions 

 between the ribs. 



The older stage of growth is marked by the sudden irregu- 

 larity of general growth and change of ornament — the radial 

 ridges becoming almost obsolete, and strong growth folds and 

 concentric striae developed. 



The ears are unequal, the proximal portions radially ribbed 

 and shagreen sculptured, the distal portions irregular and in- 

 ornate. 



Dimensions. — TImbo-ventral and antero-posterior diameters, 

 47 millimetres. 



Locality. — Upper beds at Muddy Creek. 



This species, which is related to P. consobrinus, Tate, may 

 prove to belong to JLinnites, but at present the left valves only 

 have been obtained. 



Pecten subconvexus, spec. nov. Plate xviii., fig. 2. 



Irregularly orbicular, moderately convex, produced in front, 

 radially ribbed. Eibs about 27, broad, truncated, considerably 

 elevated, becoming thinner and subacute towards the sides ; an 

 indistinct appearance of three radial plications is produced by 

 thicker ribs occurring close together in pairs. The interspaces 

 between the ribs are as wide or a little wider than the ribs ; 

 they are concentrically sulcate, the intervening elevated threads 

 are about equal in width to the sulci. Ears ? Margin of the 

 valve crenately undulate. 



Dimensions. — Antero-posterior diameter, 30'5 ; umbo-ventral 

 diameter, 31*5 ; sectional diameter of right valve, 5*5 milli- 

 metres. 



Locality. — Upper beds at Muddy Creek (J. Dennant!). 



