i68 ADDENDUM TO SPONGES 



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

 Astrosdera is genetically distinct fn)ni the true Calcaiea, in which the 

 skeleton is invariably calcite. On the other liand, it is |H>ssible that the 

 spherules have in the course of i)hylogony replaced a skeleton of calcito 

 spicules originally present In some I'haretrones a similar skeleton of 

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

 regarded as a secondary formation due to recrystallisation of the lime 

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

 Ai^trom-Uiti as the type of a new family AMroM-lcridiH\ possibly allied to 

 the rharetrones, but certainly without close aflinity with any other known 

 group of sponges " (Lister). 



A larger specimen of the same genus and probably of the same si>ecies 

 of sponge has recently (November 1890) been detected by Mr. Kirk- 

 patrick of the Hritish Museum (Natural History^ in a collection of 

 marine organisms dredged at Funafuti (Gilbert Islands). 



