ADDENDUM TO SPONGES 



lime, but the fact that it is in the form of aragonite may indicate that 

 Astrosclera is genetically distinct from the true Calcarea, in which the 

 skeleton is invariably calcite. On the other hand, it is possible that the 

 spherules have in the course of phylogeny replaced a skeleton of calcite 

 spicules originally present. In some Pharetrones a similar skeleton of 

 spherules is known (Zittel), but in such cases the spherules are generally 

 regarded as a secondary formation due to recry stall isation of the lime 

 during fossilisation. " Under these circumstances it seems better to class 

 Astrosclera as the type of a new family Astrosderidae, possibly allied to 

 the Pharetrones, but certainly without close affinity with any other known 

 group of sponges " (Lister). 



A larger specimen of the same genus and probably of the same species 

 of sponge has recently (November 1899) been detected by Mr. Kirk- 

 patrick of the British Museum (Natural History) in a collection of 

 marine organisms dredged at Funafuti (Gilbert Islands). 



