Geological Society. 167 



saurs and the lower Gauocephalous reptiles of the Carboniferous 

 series, in which, however, the vertebral centra are more widely 

 perforated. 



January 19, 1876. — John Evans, Esq., F.R.S., President, 

 in the Chair. 



" On some Unicellular Algae parasitic within Silurian and Ter- 

 tiary Corals, with a notice of their presence in Calceola sanda- 

 lina and other fossils." By Prof. P. Martin Duncan, F.R.S., 

 V.P.G.S., &c. 



After noticing the works of Quekett, Rose, Wedl, and KoUiker, 

 which refer to the existence of minute parasitic borings in recent 

 corals, recent shells, and a few fossil mollusca, the author describes 

 the appearance presented by a great system of branching canals 

 about 0-003 millim. in diameter, in a Thamnastraean from the 

 Lower Caiuozoic of Tasmania. He then proceeds to examine the 

 corresponding tubes in Goniophyllum pyramidah from the Upper 

 Silurian formation. In sections of that Coral one set of tubes runs ' 

 far into the hard structure; these are straight, cylindrical, and contain 

 the remains of vegetable matter. Neither these tubes, nor any 

 others of the same parasite, have a proper wall ; they are simply 

 excavations, the filiform alga replacing the organic and calcareous 

 matter abstracted. In some places the dark carbonaceous matter is 

 absent, and the lumen of the tube is distinguishable by the ready 

 passage of transmitted light. Other tubes run parallel to the wall, 

 and enter by openings not larger than their common calibre. But 

 there are others which have a larger diameter, and in which the 

 cytioplasm appears to have collected in masses resembling conidia ; 

 and where fossilization has destroyed much of the continuity of a 

 tube a series of dark and more or less spherical bodies may be seen. 

 In some places, especially in the spaces between the minute curved 

 dissepiments and tabulae, hosts of globular spores, with or without 

 tubes emanating from them, may be seen. In Calceola sandalina 

 corresponding structures exist sometimes, and the method of entry 

 of the parasite can be examined. The author gave two instances, 

 one of which was seen in section. A decided flask-shaped cavity 

 existed in the wall of the shell, opening outwards and rounded and 

 closed inwards. It was crowded with globular spores (oospores) ; 

 and these, where near the sides, had penetrated the hard shell, and 

 thus gave a rugged and hairy appearance to the outline of the 

 flask-shaped cavity. After noticing minute structures in a Bra- 

 chiopod included in a Silurian Coral, and in a Lower vSilurian Fora- 

 minifer, the author assorted, from the results of his late researches 

 upon the algae parasitic in Corals out of his own aquarium, 

 that the fossil and recent forms are analogous in shape, size, and 

 distribution. He considers that the old parasite resembles Sapro- 

 legnia ferox in its habit ; and as he considers that Emjiusiva, >Sa- 

 prolegnia, and Achlyn (members of the Protista) are the same 



