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On some Remarkable Spicules from the Oamaru Deposit. 



By B. W. Priest. 



(Bead April 2.1th, 1888.) 



Plate XIX. 



I take it for granted that you are all more or less well acquainted 

 with the famous diatomaceous deposit from Oamaru, New Zealand, 

 with its wonderful collection of diatoms and sponge spicules. 



In examining some of the cleaned material kindly sent to me by 

 Mr. Grove from Jackson's Paddock, a place farther up the valley 

 than that from which the original material came, I was at once 

 struck by the remarkable size and condition of the sponge spicules. 

 I should think examples of almost every species of silicious sponge 

 is represented ; most of them are well preserved, but a great many 

 show different stages of decay and peculiar states of disintegra- 

 tion. 



When it first occurred to me to bring this communication before 

 you, I thought that I had, to a certain extent, discovered something 

 new, but on reading over several papers on the subject of sponge 

 spicules I had to fall back on the old adage that there is nothing 

 new under the sun. At the same time, wanting more information 

 on the subject, and being of peculiar interest, I have ventured to 

 bring it forward. 



In order that you may understand what I have to say regarding 

 the subject, I must start by telling you a little on the development 

 of the spicules. 



It appears that the sponge spicule is developed in a cell, and 

 may be often seen in the embryo sponge, which cell becomes lineally 

 extended in opposite directions, or begins to put forth more or less 

 points in a radiating direction, whereby what is called the central 

 canal of the spicule is formed ; and upon the tubular prolongations 

 as they extend is deposited, in concentric layers, silico- or calcareo- 

 albuminous material of which the spicule may be composed, the 

 extremity of the tubule or central canal only becoming covered 

 when the fundamental form of the spicule is completed. Thus you 



