390 
PROCEEDINGS OF THE SOCIETY. 
described by Elirenberg as constituting a distinct species by themselves. 
These forms are frequently met with in many of the American deposits. 
18. Kittonia elaborates. — From deposit at Oamaru, N.Z. This is 
a particularly fine form, and is not very uncommon in this deposit, but 
when found it is generally more or less broken. I have never found 
it other than as a single valve, but I have occasionally found smaller 
valves differing considerably from those now shown. This slide shows 
the front and side views of this form. 
19. Navicula disciformis. — From artesian well, Cambridge, Mary- 
land. This is a very curious and small form, not very rare in this 
deposit, and I was fortunate enough to find a frustule which I have 
mounted edgewise. 
20. Odontotropis cristata. — From “ Cementstein,” Mors Island, Jut- 
land. This diatom is a large one, but I have been unable to mount it 
as a frustule, because the valves fall away from each other when placed 
in a drop of water to free them from dirt. 
21. Porodiscus interruptus and Craspedoporus elegans. — From the 
Oamaru deposit. Described by Messrs. Groves and Sturt in the Journal 
of the Quekett Club. 
22. Pseudo-rutularia monile. — From deposit at Oamaru, N.Z. The 
central pair of valves belong to two opposing frustules ; I have never 
yet found a complete frustule of this form. It is frequently the case 
that the number of cells on one side of the large central one is one 
more than the number on the other side. Messrs. Grove and Sturt, as 
well as Herr Grunow, incline to the belief that this is a species of 
Hemiaulus. There is only a single species in this genus, if it holds 
good. 
23. PterotJieca aculeifera. — From “ Cementstein,” Mors Island, Jut- 
land. This very curious form is regarded by some as belonging to a 
larger genus, viz. Pyxilla. The three central diatoms show the manner 
in which the valves of opposing frustules were connected by their 
branched processes. 
24. Butilaria capitata. — From “ Cementstein,” from Sendai, North 
Japan. The Cementstein from which this diatom was obtained is very 
rich in new and fine forms. This slide shows how the frustules of this 
form are connected in chains. The lower diatom is a side view of a 
valve showing the capitate ends from which the species takes its name. 
25. SticJiotiscus caltfornicus var. areolata. — From deposit at Oamaru, 
N.Z. Showing valves laid flat and a single frustule on edge in the 
centre. 
26. Syndetoneis amplectans, fossil. — From Oamaru, N.Z. This is a 
perfect specimen of a small and curious form from the Oamaru deposit. 
It is not extremely rare, but is generally damaged more or less. The 
diatom shown consists of two valves of opposing frustules, each valve 
having a central rod, at the end of which is an eye, set at right angles 
to it, the rod of the other valve passing through. These rods slide on 
each other, and the valves cannot be separated without breaking one of 
the central rods. 
27. Terpsinoe intermedia .— From Salt Marshes, near Mobile, Alabama. 
The upper centre form on this slide is very peculiar ; it is the opinion 
of some that in the process of reproduction the larger frustule, which 
