E/OPER^ on Biddulphia. 
23 
connected with Tabellaria and Grammatophora, as proposed 
by Kiitzing. Ehrenberg^s genus Hemiaulus I have had no 
1a. 1 1 z a, 
1 a and h. Side and front view of Biddulphia turgida. 
2 a and h. Ditto, ditto, Biddulphia rhombus. 
H a and h. Ditto, ditto, Triceratium striolatum. 
4 a and b. Ditto, ditto, Amphiteiras antediluviana. 
5 a and b. Ditto, ditto, Amphipentas ? 
opportunity of examining, but his figures and descriptions 
lead me to suppose it is distinct from Biddulphia, but that 
the position assigned to it by Kiitzing in the same group is 
probably correct. 
The study of the valves of Biddulphia, along with its allies, 
Amphitetras, Isthmia, and Triceratium, are of considerable 
interest to the microscopical observer, as from the size and 
distinctness of the reticulations in some of the species, we are 
enabled to form a clearer idea as to their structure, than 
from an examination of forms which require high magnifying 
powers and careful illumination to elucidate. I believe it is 
generally admitted that the markings in Isthmia and Biddul- 
phia pulchella are of the same nature, and from some 
interesting experiments of Professor Bailey on the action of 
hydrofluoric acid on the desiccated valves, we learn that in 
Isthmia the " spots gradually become holes as the valves 
dissolve j"^ we may therefore safely conclude that the siliceous 
matter is thinner in those parts, than in the general frame- 
* See 'Sil. Jour.,' vol. ii, new series, p. 349. 
