Vol. 56.] FROM THE EOCENE OE VICTORIA. 5$ 



or grown together. The main skeleton of the sponge is of reticulate 

 anastomosing fibres, built up of four-rayed spicules in which the 

 apical ray is elongate, tapering and pointed, usually definitely 

 orientated and frequently projecting, spur-like, beyond the fibres, into 

 the mesh-interspaces. The facial rays are straight or curved, with 

 truncate or expanded ends, which are not only closely fitted to the 

 surfaces of adjoining spicules, but firmly cemented or fused as well. 

 The fibres are invested with a calcitic pellicle, having a minutely 

 spined outer surface. Slender rod-spicules are abundantly distri- 

 buted in the interspaces of the mesh. A system of exeurrent canals 

 extends from the lower portion of the sponge in a generally vertical 

 direction and open at the summit. 



The characters of the type-species, P. Halli, are given in the 

 foregoing description. The specific name is in honour of Mr. T. 

 S. Hall, M.A., of Melbourne University, to whom I am indebted 

 for the opportunity of studying this unique form. 



In addition to the typical example there occur, in the collection of 

 sponges sent me by Mr. Hall from beds of corresponding age at 

 Flinders (Victoria), some small specimens which probably belong to 

 this species ; but, owing to the nearly complete obliteration of their 

 spicular structure, they cannot be fully identified. The sponges in 

 question are simple, rounded or turbinate, the base flattened or 

 supported on a short blunt pedicel (PI. Ill, figs. 2 & 3). They are 

 from 6 to 10 mm. in diameter. Thin bands of dermal layer are 

 present near the base, and transverse platforms are shown in 

 the interior. The disposition of the mesh-fibres and the canals is 

 the same as in the type of the species, but no comparison of the 

 spicular structure can be made beyond that rarely the spined apical 

 ray of a mesh-spicule is distinguishable. 



Distribution. — The type-specimen is from Eocene clays l ex- 

 posed in the banks of the Moorabool River at Griffin's Farm, 

 north-west of Geelong ; also from Polyzoal Limestone 2 of Eocene 

 age at Flinders (Victoria). Collected by Mr. T. S. Hall. 



Genus Bactronella, Hinde, 1883. 

 emend. Catal. Poss. Spong. Brit. Mus. p. 205. 



This genus was proposed to include some small fossil calcisponges 

 of Jurassic age, which had been placed as polyzoa under Ceriopora 

 clavata, 3 Goldfuss. The microscopic structure of the specimens on 

 which the genus was based was too imperfect to allow of a proper 

 diagnosis; it was seen to differ from that of Pharetron calcisponges, 

 and the genus was regarded as incertce sedis until its characters 

 were more clearly ascertained. The discovery of some well-preserved 



1 See Hall & Pritcbard, ' Notes on the Lower Tertiaries of the Southern 

 Portion of the Moorabool Valley ' Proc. Roy. Soc. Vict. n. s. vol. iv (1891) p. 9 ; 

 also 'G-eology of the Lower Moorabool ' ibid. n.s. vol. x (1897) p. 43. 



2 Eep. Austral. Assoc. Adv. Sci. vol. vi (Brisbane, 1896) p. 348. 



' Petref. German.' pt. i (1833) p. 36 & pi. x, figs, c-f (non a, b). 



