NATURAL HISTORY SOCIETY OF GLASGOW. 103 



runs through the limestone strata at this place, the direction being 

 from N.N.W. to S.S.E. This dyke has not caused much displace- 

 ment of the strata ; but the faces of the vertical joints of the 

 limestone in the quarry are seen to be beautifully marked with 

 slickensides, the striae of the polished surfaces running in 

 horizontal directions. By the percolation of water impregnated 

 with carbonic acid along the faces of these joints, the limestone has 

 been curiously eroded into narrow gutters or fissures of a few 

 inches in depth, and it is from the decomposed material filling these 

 fissures that the sponge spicules are to be obtained in excellent 

 preservation. Besides these, other organisms which the limestone 

 contains are to be found in the deposit, many of the species of 

 Productus having their spines still attached to the shell, and 

 weathered quite free from the matrix. The sponge spicules, 

 which are of various sizes, from one-twelfth to three-eighths of 

 an inch, are of tri-radiate and quadri-radiate forms, a few being 

 stellate, while more rarely others are fluke — or anchor-shaped. The 

 rays of the various spicules generally terminate in points, but 

 certain of them terminate in rounded knobs. They agree in 

 general form with many of the silicious spicules found in sponges 

 which still live in our present seas. ]\Ir Young stated that 

 the Carboniferous spicules from Dairy are being investigated by 

 Professor Young and himself. They had provisionally placed 

 them in the genus AcantJwsjiongia of M'Coy, naming the species 

 after the discoverer, Mr Smith. In the same deposit is found an 

 abundance of another organism termed Serjnila parallela of M'Coy. 

 These consistof bundles of tubular silicious rods, varjdng in diameter 

 from the size of fine hairs to one-sixteenth of an inch. This 

 organism, which is not uncommon in other localities in the lower 

 limestone strata of Scotland, is now believed not to be a species of 

 Serimla, but to be somewhat closely, if not generically, related to 

 the recent Hyalonema, one of the glass rod sponges. In strata, 

 where all the other organisms exist in a calcareous condition, 

 Serpula imrallela is always made up of brush-like silicious bundles. 

 This being the case, Dr Young and himself had provisionally 

 placed it in the genus Hyalonema, naming it H. imrallelum. It 

 has been thought probable that this glass rod sponge and the 

 spicules of the Acanthospongia may belong to the same organism, 

 but they had failed as yet in finding any specimens that showed 

 the organic connection of the two forms. 



