Lauder^ on Marine Diatomacece. 79 
lower valve and with the axis of the frustule. Spines, two in 
-j-oVo''; striae resolvable into clots ; lateral view roundly oval. 
C. coarctata, n. sp. Filaments composed of qnadrangular_, 
closely approximated frustules, without fenestra_, with stout, 
spinous, and striated awns arising from within the angles 
(fig. 8). 
Filaments straight, with the terminal awns hexagonal, 
tapering at each end, shorter and stouter than the others, 
with serrated angles, and incurved ; the other av/ns quadran- 
gular and spinous, those nearer the end ones coarsely spinous 
and curved on themselves, lihe the crook of a crosier or 
sheep-hook ; the rest more slender, minutely spinous, and 
simply recurved. Side view oval, with two triangular depres- 
sions for the insertion of the awns. Breadth of frustule, 
-y-iV' } of terminal awn, ttj-ott''- Tliis species is often covered 
with a species of Vorticella, which, when in full life and 
motion, gives it a very extraordinary and outre appearance. 
C. denticuJata, n. sp. Filaments with quadrangular frus- 
tules, long, quadrangular, delicately spinous awns, which are 
situated on surface of valves, suddenly expanding at the base, 
and furnished on the inner side with a notch-like tootli 
(fig.9). 
Filaments straight; awns parallel, and at right angles 
to the axis of the filament, expanding suddenly a little 
before insertion, like the bowl of a pipe, and usually 
having a small process on the inner side, giving it a still 
more striking resemblance to a pipe. This process seems to 
be for the purpose of articulation with the contiguous frus- 
tule, as it is not present in the terminal awns. Side view 
oval, with the insertions of the awns strongly marked. 
Breadth of frustule, -^^^'^ Length of awn, 3^"/'; breadth, 
about 3VbV'- 
C. Tostratttj n. sp., resembles C denticulata, but is usually 
smaller, without the articulating process of the awns, and the 
valves have a tubular, conical, central process, which articu- 
lates with the similar process of the adjacent valve (fig. 10).^^ 
C. protuberans, n. sp. Filaments with minutely spinous 
awns, having between them a mamilliform protuberance, 
which projects into the fenestra (fig. 11). 
^ Filaments straight, with very slender, delicate, interme- 
diate awns, and stouter and shorter terminal ones. Valves 
with a central projection; compressed oval in the side view. 
Breadth of frustule, about y^-jy'' ; length of terminal awns, 
about -riu". 
* This form is regarded as a variety of C. denticulata by Mr. Lauder, but 
we believe the differences pointed out by him sufficient to distinguish them, 
— J. R, 
