TRANSACTIONS OF SECTION C. 663 



evidently one of the most highly specialised Acauthodiaus, and showed that among 

 these primitive fishes, as among modern Teleosteans, there was a tendency for the 

 pelvic pair of tins to become displaced forwards in the higher types. The author 

 had already described the same phenomenon in the typical family Acanthodidae. 



4. 0)1 some Dinosaurian Bones from South Brazil. 

 By A. Smith Woodward, LL.D., F.R.S. 



The author had received from Professor II. von Jhering a few cervical vertebrae 

 and phalangeal bones of a reptile discovered by Dr. Fischer in red roclis in the 

 province of Kio Grande do Sul, Brazil. He described these remains, and suggested 

 that they belonged to a short-necked Dinosaur. The ungual phalanges were 

 especially remarkable, apparently unique, in being deeply concave on their inferior 

 face and having a very sharp rim. Comparison seemed to show that, among known 

 Dinosaurs, the cervical vertebra; most closely resembled those of Euskelesaurus 

 from the Karoo Formation of South Africa. The newly discovered bones were 

 therefore probably the first traces of the Gondwana-land terrestrial fauna, the 

 discovery of which had long been expected in South America. 



5. On Bolyzoa as Rock-cenienlmy Organisms. 

 By J. LosiAS, A.K.C.ti., F.G.S. 



Among the specimens of sea-bottoms recently brought from the Gulf of Mauaar 

 by Professor Herdman were about twenty samples of ' calcretes.' They were 

 broken off by pearl divers from the parent masses which form rocky platforms, 

 locally called ' paavs,' in many parts of the gulf. They all occur in shallow water 

 at depths varying from 2^ to 10 fathoms. 



The majority of the specimens were sandstones cemented by carbonate of lime, 

 hut occasionally compact limestones, sometimes phosphatic, and coral rock were 

 brought to the surface. 



All the stones were thickly incrusted with organisms such as polyzoa, nuUi- 

 pores, worm tubes, sponges, &c. 



While the importance of nullipores as agents in binding grains of sand has 

 been recognised, the work of polyzoa has not hitherto been recorded. The thin 

 calcareous walls of polyzoa so readily break up and lose their structural characters 

 that it is only when very recent samples are at hand we can obtain criteria which 

 determine their former presence. 



On examining a thin slice of calcrete with recent colonies on the outside we 

 find the surface layer shows sections of the cells arrayed like bricks in a wall and 

 containing the zooid in the interior. The spines and avicularia bordering the cells 

 entrap and retain sand grains drifting over them, only retaining those which fit 

 into the spaces they provide. Thus a sifting takes place, and we see above the 

 outer layer of cells grains of sand and foraminifera of fairly uniform size caught in 

 the manner described. The cells forming the next layer below are nearly all filled 

 with grains : the base and side walls are complete, but the top covering has broken 

 down to admit the sand grains, carrying with it the thin calcareous wall and the 

 cliitinous operculum. Several layers of this kind succeed towards the interior, but 

 as we proceed further, the walls become less prominent owing to secondary calcite 

 being deposited, which grows in tiny scalenohedra towards the interior of the cells, 

 and finally fills up all the corners and other spaces. When this stage has been 

 reached we only have a thin dark line marking the junction of the double side 

 walls, the roughly linear arrangement of uniform grains and occasional remains of 

 the chitinous opercula to indicate the former presence of polyzoa 



Further towards the interior ot a thick block even these guides become less 

 distinct; but the grains still retain a rudely linear arrangement, and cells which 

 escape being occupied by a grain are filled with calcite. 



