92 
Helations and Differences. — In its size iliis species approaches Avicu- 
lopecten Sashachii, d’Archiac and du Vernenil, but it is widely separated from 
it in the form and number of its ridges, and above all by the presence of well- 
marked growth lamellse on its outer surface. 
Horizon and Locality. — The single fragment I have been able to 
examine was collected on the banks of the Macleay Hiver; it is in a sandy 
limestone, grey or brownish in colom. Although I place the species I have 
just described among the Devonian species, I ought, however, to observe that 
I have no certain evidence to enable me to affirm positively that it belongs to 
this Palaeozoic epoch. I am guided only by the appearance and the nature 
of the rock and the presence in the neighbourhood of the same locality, but 
in a slightly different rock, of Favosites polyniorplia, Goldfuss. New facts 
will be necessary to solve definitely the fact I have just stated. 
PTERINEA, Goldfuss. 
Pterinea laminosum, L. G. de Koninch. 
PI. Ill, Pig. 12. 
Shell slightly transverse and a little oblique, contour suborbicular ; 
beak small and situated at the anterior third of the cardinal margin ; right 
valve a little, and rather unequally, arched, slightly depressed towards the 
posterior portion of the ventral margin ; the posterior wing fairly developed 
and triangular and connected to the median portion of the valve along a 
slightly marked sinuous line; the outer surface is covered by ten rather 
thin concentric lamellse, a little irregularly distant from one another and 
projecting but little. The shell is fairly thick in comparison to the small 
size of the shell. The left valve, of which I have been able to examine only 
a small portion, appeared to me to be flat. The hinge is unknown to me. 
Dimensions. — Length, ten millimetres ; width, twenty-one millimetres; 
thickness, about five millimetres. 
Delations and Differences. — I know no species comparable to this and 
with which it might be confused. 
Horizon and Locality. — A single specimen has been found in the 
argillaceous limestone of the Yass District. 
