— i = 
fessor Dr. Zittel of the Royal Paleontological Museum 
of Munich. — I therefore resolved to study my fos- 
sil spicules at Munich, and on my arrival in that city 
I obtained from Prof. Zittel not only the freest oppor- 
tunities for examining the rich collection of sponges 
in the museum, as well as the numerous microscopical 
preparations which had been made to illustrate their 
minute structure, but at the same time received from 
him the most cordial support and assistance in the pro- 
gress of my work, for which I desire to express my heart- 
iest thanks. I am further indebted to Prof. Zittel for 
the gift of a small quantity of material, rich in sponge 
spicules, from the upper Cretaceous Formation of Coes- 
feld in Westphalia which yielded me a great variety 
of forms of great value, from their beautiful state of pre- 
servation, for comparison with those from Horstead. 
The time involved in describing these sponge spic- 
ules has been greatly prolonged by the necessity of 
making micrometer measurements of all the forms, not 
only in order to be able to make comparisons of their 
dimensions with those of spicules described in other 
works, but also to be able to state the real size of 
these fossils and thus allow a true idea to be formed 
respecting them. I have stated the measurements 
in millimetres and decimal parts of the same, so as to 
avoid giving to those students of sponges who make 
use of this sczentific scale, the inconvenient task, 
which I have myself experienced, of reducing into mil- 
limetres the fractional or decimal parts of the English 
inch, in which the measurements of these small objects 
have been expressed by most English authors who 
have described them. 
For the faithful representations of these spicules, 
