PROCEEDINGS OF THE SOCIETY. 
391 
is the younger, whilst being formed from the contents of two much 
smaller frustules, has become silicified and fixed in one of the valves 
of the smaller frustules before the contents of the valve had quite 
escaped. I have found many large frustules with a small valve attached, 
but I have never found one with tivo small ones adhering. The small 
valve cannot be detached without injury either to it or the large frustule 
or valve. 
28. Triceratium castellatum var . fracta. — From deposit at Oamaru, 
N.Z. This slide shows a frustule in the centre with four valves sur- 
rounding it. 
29. Section of “ Cementstein ” from Mors Island, Jutland, Denmark. 
The Jutland “Cementstein” is very hard, and is admirably adapted for 
section purposes. A book by Messrs. Prinz and Van Ermengem gives 
some information as to what can be seen in sections of this “ Cement- 
stein.” 
30. Diatoms from “ Cementstein ” from Mors Island, Jutland. This 
slide gives an idea of the forms to be found in this deposit. There are 
several species of Trinacria , triangular forms with long processes at the 
corners, the end of each process terminating in a pair of small claws. 
Solium exsculpatum is very similar, but small and square. Many forms 
in this deposit are sometimes found in rather long chains. 
31. Diatoms from Howard’s Grove, Richmond, Va., fossil. This 
slide is principally of interest in showing something of the variations in 
size of different species. It shows a cast “ hoop ” of one of the larger 
Coscinodisci with twelve smaller forms, all of different species, arranged 
within the hoop ; they do not touch each other nor the hoop, which is 
less than 1/112 in. in diameter. This is not an extraordinarily large 
diatom, for I have found forms as much as 1/40 in. across. 
32. Spread-slide of fossil diatoms from Richmond, Ya. Among 
other forms there are many frustules of Stephanopyxis corona showing 
the dissimilarity of the two valves composing it. 
33. Type slide of 65 forms from Santa Monica, S. California. This 
is a sample, by no means complete, of the forms to be found in about a 
pound weight of this material. When mounting type slides, I arrange 
the diatoms in squares set diamondwise, thus placing them as close as 
possible while keeping them in symmetrical order. The slide shown 
has the diatoms arranged in a square of 8 (64), with a very small one 
placed in the centre, making 65 in all. 
34. Type slide of 121 forms from deposit at Williams’ Bluff, Oamaru. 
This slide shows the great variety of forms in this deposit. The diatoms 
found in this deposit were described by Messrs. Grove and Sturt in the 
Journal of the Quekett Club. 
35. Type slide of 80 forms of diatoms, with the name of each diatom 
photographed below it. Mounted by Herr M oiler. This is the only 
slide exhibited by me this evening not mounted by myself. 
Mr. J. J. Vezey read a short note by Mr. E. B. Stringer supple- 
mentary to his paper on Photomicrography which was read at the 
Meeting of the Society in December last, and published at pp. 174—9 of 
the number of the Journal for April 1898. 
Mr. T. C. White thought it would be most interesting if Mr. Stringer 
