182 DE. HINDE AND ME. HOLMES OlST SPONGE-EEMAINS 



other fossil and existing sponges. But as recent sponges are 

 mainly classified according to the characters of their spicules, we 

 are able, from the study of these fossil forms, to gain a know- 

 ledge of the genera and species of these organisms represented in 

 this rock. The excellent state of preservation of the spicules 

 in this material is a great advantage for their study, and still 

 more important is the fact that very many of the minuter forma 

 or so-called flesh-spicules have been preserved. These latter are 

 of very rare occurrence in the fossil state, and their number and 

 variety of form in this deposit exceed by far what has hitherto 

 been recorded. 



A comparison of these Tertiary New Zealand spicules with 

 those of recent sponges described by Carter, Oscar Schmidt, 

 Bowerbank, and other spongologists, and more especially with 

 those figured in the ' Challenger ' Reports on these organisms, 

 shows on the w^hole a remarkable similarity between them ; the 

 difierences are mainly in details of size and form, such as would 

 indicate specific rather than generic or family variation. A 

 striking feature in the Gamaru deposit is the extraordinary 

 commingling of representatives of different divisions of sponges 

 to an extent greater than has been proved to exist in other 

 similar fossil deposits. 



To a great extent our comparison of the fossil with receat 

 spicules has been necessarily limited to those of known sponges, 

 for no attempt has been made to study or describe the detached 

 spicules which are so numerous in recent deep-sea deposits, and 

 from what we have seen of those obtained by the ' Egeria ' it is 

 certain that many belong to sponges which are as yet unknown 

 to science. 



Many of the forms in the Oamaru deposit have their nearest 

 existing allies living in the Indian Ocean and in the Australian 

 Seas, but the relations of some others are now only known from 

 areas widely separate from New Zealand : thus, for example, the 

 genus Guitarra, Carter, fairly well represented at Oamaru (PI. XI. 

 figs. 1-7), has hitherto only been known from the Grulf of Mexico 

 and the North Atlantic. 



Though it is probable that most of the spicules referred to 

 later on belong to species not hitherto described, it has not 

 seemed desirable to apply trivial names to them except in 

 a few instances where the forms are very markedly different 

 from those of species already known. We propose to treat these 



