BY E. F. HALLMANN. 413 



spectively Clathria indurata and C. spicata. Also, Plectispa ele- 

 gans is falsely represented by a specimen of Echinoclathria arho- 

 rea* But with these exceptions no example labelled with tlie name 

 of any of the species enumerated above is to be found either in 

 the Australian Museum or among the fragments from the British 

 Museum. Occurring among the latter, however, tliere is an un- 

 attached label inscribed with the name Clathriodendron irregularis, 

 so that this species is in all probability represented by an example 

 in the British Museum. 



Myxilla jacksoniana. (Text-fig. 16). 



Introductory. — As the type of this species I take the sponge re- 

 presenting it in the British Museum, which agrees fairly closely 

 witli the original description; the ostensible type-specimen in the 

 Australian Museum is mislabelled, being in reality an example of a 

 species of Gellius, closely related to G. raphidiophora. Having 

 only a small fragment at my disposal I am unable to say any- 

 thing concerning the outward characters of the species. The 

 original description states in reference thereto merely that the 

 sponge is massive, lobose, and provided with conspicuous oscula; 

 but it may be that this statement is incorrect, since it is one that 

 would apply very well to the false type-specimen. 



Description. — The skeleton is a renieroid reticulation with for 

 the most part quadrangular and triangular meshes, the sides of 

 which are formed each of one to three (or rarely more) spicules; 

 the spicules have a not very orderly arrangement, and in many 

 places, as a consequence, the reticular pattern is ill-defined. Defi- 

 nite fibres are apparently not developed, and spongin is indis- 

 cernible. The spicules of the mesh-work are styli, together with 

 a very appreciable proportion of shorter and stouter stronglya 

 which undoubtedly are derivatives of the styli. Occurring scattered 



*That my identification of this species with Lendenfeld'a Plectispa 

 arhorea is correct, is supported by the fact that the MS. synonym of 

 Plectispa arborea is, according to the key-list, ^'Plectochalina hal7Jie"—a. 

 name which would be more appropriate in its application to Echinoclathria 

 arborea (owing to the species' resemblance in reticulate structure to Halmt 

 nidus-vesparum) than to any other species described in the Catalogue. 



