— 7 — 



fessor Dr. Zittel of the Royal Palceontological 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 scientific 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. 



