30 
DoNKiN^ on Marine Diatomacece, 
species in the genus Epithemia. With this opinion^ I may 
mention, Professor Gregory concurs, while, on the other hand, 
Mr. Roper considers it to be a Nitzschia. But notwithstand- 
ing the high esteem in which I hold his accuracy and expe- 
rience as a scientific observer, I cannot reconcile my views^ 
on this point, with his. It seems to me, that this curious, and 
somewhat anomalous, form is without those essential generic 
peculiarities of the true Nitzschm, namely, compressed 
valves, with a keel to each, and its accompanying line or 
lines of punctse. 
Amphora, 
In describing the following Amphorse I have adopted the 
terms dorsal and ventral, as employed by Ehrenberg. These^, 
though discarded by Mr. Ralfs and Professor Smith, are 
essentially necessary for the description of several recently 
discovered species of the present genus, in which the dif- 
ference of structure, observable in each of these surfaces, is so 
great, that when a frustule is seen in a focus first shewing the 
one, and afterwards in a diff'erent focus exhibiting the other, 
the diff"erence of appearance is so great that an observer, un- 
aware of this fact, might readily suppose that he was looking 
at two widely different forms. This is well illustrated in fig. 
15 a and b. The term hoop I have also used, in the same 
sense as employed by Dr. Carpenter,^ to designate the sili- 
ceous plate intervening between the margins of the opposed 
valves. It will be observed that I have employed these 
terms, in the same sense, in reference to Epithemia marina. 
15. A, litoralis, n. sp. — Form on F. V. oval, with truncate 
extremities. Hoop on dorsal surface broad, oval, slightly 
constricted, and marked with seven or more longitudinal lines 
of linear, transversely set punctse; hoop on ventral surface 
linear, narrow, widest in the middle and at the extremities, 
hyaline. Length from 0-002" to O'OOS"; breadth from 
0-0008" to 0-0012". S. V. dorsal margin arcuate, ventral 
linear ; extremities obtuse ; longitudinal line gently curved, 
situated some distance from the ventral margin, and dividing 
the valve into an outer and inner compartment; central 
nodule expanded into a strong, opaque, transverse bar, reach- 
ing to the dorsal margin. Striae very distinct, moniliform ; 
those of the inner compartment the finer. 
The present species is evidently a member of Professor 
Gregory's group of complex Amphorce. The complex structure> 
* ' On the Microscope/ p. 303. 
