Mr. R. Gurney on Scapholeberis aurita. 631 
whole length of the valve, but near the anterior end is con- 
tinuous with an obliquely transverse ridge which joins the 
external ridge (fig. 1). There is thus marked off in front a 
Fig. 1. 
PEPE om ie 
SS Seaeeeeee 
more or less triangular area which is somewhat depressed 
and strongly reticulate. The remaining portion of the valves 
in S, aurita is not reticulate, but simply punctate. 
Seen from the side (fig. 2) the shell-margin ig almost 
straight, but with a prominent projection anteriorly corre- 
sponding to the point of union of the transverse and external 
longitudinal ridges. 
So far the two species are in essential agreement, but they 
differ strikingly in the armature of the flattened area. In 
S. mucronata this area is provided with a number of pecu- 
liarly arranged scales and modified sete (see Scourfield 
pl. ii. fig. 1), but nothing of the kind occurs in S. aurdta, 
Here the flattened area shows no sete whatever, and the setae 
which fringe the inner edge of the valves are quite simple 
and delicate. On the other hand, careful examination of the 
inner longitudinal thickening shows a series of small upwardly 
41* 
