30 Greville_, on New Species of Campy lodiscus. 
other new forms_, was no larger than a walnut. This may 
serve as a hint to conchologists into whose hands such shells 
as Spondyli, and others favorable to the incrustation of 
zoophytes^ come in a rough state, not to throw away the 
scrapings and cleanings which may be necessary to prepare 
them for the cabinet. No locality was given with the shell 
in question ; but the diatoms parasitic upon it furnish almost 
conclusive evidence that it came from the West Indies. 
C. marginatus, Johnst. ? Mic. Journ./ vol. viii, PI. I, 
fig. 11). — Valve nearly circular; canaliculi 5 in '001 less 
in length than half the radius, forming a narrow marginal 
band ; central area elliptical- oval, filled with close, transverse, 
moniliform striss, interrupted by a narrow median line of 
blank space. Diameter '0023". "^Fig. 2. 
In scrapings of conch-shells, Nassau, New Providence; 
R. K. G. Californian guano ; T. G. Rylands, Esq. 
On this diatom, examined and drawn many months ago, 
I had bestowed the MS. name oi concinnus ; but it is pro- 
bably the same as Dr. E. Johnston^s C. marginatus, published 
in vol. viii of the ' Journal of Microscopical Science.^ I am 
not, however, quite certain of this. There is a great dif- 
ference in regard to size ; his example x 300 diameters being 
much larger than mine x 400. I have seen several speci- 
mens all agreeing most closely in every particular. The 
introduction of my own figure in this place may serve to 
throw some light on the question, and to confirm the species. 
C. iynperialis, n. sp., Grev. — Valve circular ; canaliculi 
more than one third the length of the radius, 3 in "OOl", 
forming a marginal band; central area broadly elliptical, 
filled with narrow, transverse, moniliform striae, interrupted 
by a narrow median line of blank space. Diameter '0055". 
Fig. 3. 
In scrapings of conch-shells, Nassau, New Providence. 
The shell- cleanings in which I was so fortunate as to 
detect this truly splendid species, were kmdly presented to 
me by Mr. George Norman. After cleaning and preparing 
them by the usual processes, I obtained sufficient material 
for mounting nearly twenty slides, and it is remarkable that 
almost every slide contains something peculiar to itself. In 
one slide only does a perfect example of the species now 
figured occur. In the general appearance of the marginal 
band it resembles C. limbatus of De Brebisson, but difiers 
materially from that diatom on a closer examination. There 
is a sort of minute secondary band, composed of a series of 
bifid segments, alternating with the canaliculi at their base, 
which gives a highly ornate character to the margin. The 
