Greville^ on the genus Auliscus. 
43 
witli a circle of eight visible processes. It seems doubtful^ 
therefore, whether some species may not actually possess three 
or four processes. 
^ Radiating lines costate (not punctate) . Valve mostly 
oval, or slightly oval ; in the first three species occa- 
sionally circular. 
Auliscus sculp tus (Smith), Ralfs; valve circular or inclining 
to oval, with indistinct umbilicus, and two lateral rounded 
depressions; costee in four sets, radiating from the centre, 
two of them converging to the processes, and, along with the 
rounded depressions, forming a well-defined 4-lobed figure or 
quatrefoil; the costse within the depressions strong, few, un- 
equal, quite smooth (no apiculi), and appearing to terminate 
abruptly within the edge of the cavity; marginal costee strong, 
distant; diameter -0020" to '0035''. (Pis. II & III, figs. 1—3.) 
Auliscus sculptus, Ralfs in Pritch. Inf., 1861, p. 845, pi. vi, 
fig- 3. 
Enpodiscus sculptus, ' Sm. Brit. Diat.,^ vol. i, p. 25, pi. iv, 
fig. 42; ^Mic. Diet.,' pi. xii, fig. 31. 
Hah. Poole Bay, 1851 ; Professor Smith ; Barking Creek, 
on the Thames, F. C. S. Roper, Esq.; Ipswich, E. Kitton, 
Esq.; Penzance, J. Ralfs, Esq.; Westport Bay, Ireland, G. M. 
Browne, Esq. 
I have been quite unable to discover any strongly definitive 
character between this, the earliest known species, an'd the 
one immediately following; and those naturalists who are 
influenced by what has been called a " righteous horror'-* of 
uncertain species would, no doubt, be in favour of their union ; 
but in that case we should have fig. I at one end of the series^ 
and fig. 6 at the other, which would surely be an extreme 
view. The single desire to study these two species, and the 
singular deficiency of materials, has alone caused a twelve- 
month's delay in the preparation of this small monograph. 
I have at length, however, in addition to an ample series of 
A. ccelatus, had an opportunity, through the kindness of Mr. 
T. G. Rylands, and other friends, of examining a considerable 
number of the present species ; and the result is, on the 
whole, satisfactory to my own mind, although it may not be 
equally so to others who have not had the same opportunity 
of tracing minute differences. It will be at once perceived 
that there is no difficulty in referring specimens, as they ordi- 
narily occur, to their respective places. It is only where 
exceptional frustules approach each other that any embar- 
rasment is experienced. The principal features in A, sculp- 
