19 
Left valve convex ; anterior cardinal margin oldique, with feeble 
scol)inate lamellm ; posterior cardinal margin long and inwardly bevelled ; 
anterior and ventral margins rounded ; posterior alation wing-like, convex in 
the middle, flattened above, separated from the body of tlie shell by an 
oblique longitudinal depression ; umbo small, pointed, and slightly over- 
hanging the area, which is wide medianally, and linear posteriorly. Pyriform 
cbondropbore obliquely sboe-born shaped, large, with concentric resilium 
furrows ; transverse cbondropbore long, with parallel resilium furrows ; 
cardinal socket variable, in some individuals well marked, in others not so; 
hepatic fossa transverse and deep. Adductor impression large, subcentral 
in position, and subreniform in shape, concentrically lined ; circlet of 
supplementary pits sometimes present. Sculjiture. — In the right valve 
consists of a very large number of tine radiating costae, frequently with a 
liner costa interpolated between every two, crossed by broad laminae of growth 
and fine, delicate close inbricating lines. The left valve is covered with 
similar costae, but much stronger and coarser, and a like concentric structure, 
but the primary costae on the posterior third of the valve proper, and on the 
posterior alation, rise at their intersection with the broad laminae of growth 
into feeble fistulose spines. 
Ohs . — The shells of 31. rejlecta are of larger si/.e than those of the 
type species, 31. Bavkhji, the cardinal margin longer posteriorly, whilst the 
posterior alation of the left valve is raised on a portion of its surface into an 
oblique lobe, and the scobinate lamellae of the anterior cardinal margin are 
much less developed. The costm of the left valve far outnumber those of 31. 
Barklyi, a specimen now before me supporting no less than sixty-two; hut the 
distinction into primary, secondary, and perha])s tmTiary, although it exists, 
is not nearly so marked as in the type species. On the other hand, contrary 
to my former expressed opinion, the primary costm, support a few fistulose 
spines. The convexity of the left valve is more than I had formerly 
conceived, from the imperfect material then before me, and does not 
materially differ from that of 31. Barklyi. 
A very instructive examjde in the form of a young shell (PI. I, 
Pig. 3) is in the Macleay Museum from the Grey Langes. The costm are 
all very sharp and distinct, and in this case are certainly of three orders, 
primary, secondary and tertiary. It is to be noted, however, that the tertiary 
are only developed on the posterior half of the valve In this young condition 
the fistulose spines are not developed. 
