208 



HARDWICKE'S SCIENCE-GOSSIP. 



[Dec. 1, 1870. 



those belonging to the Brachiopoda. Indeed, these 

 shells far outnumbered the ordinary couchifera, 

 whereas at the present time the latter are equally 

 in the majority. 



Among the commonest of the shells I remember, 

 were several species of Spirifer, Stringoceplialus, 

 &c, and also Clymenia, Megalodon, and others. The 

 last was a lamelli-branchiate mollusc, allied to'the 

 oyster and mussel of the present day. Among the 

 corals there abounded in Devonshire the Favosites 

 polymorpha, or "many-sided" coral, as well as 

 Heliolites, or " suu-coral," Stromatopora, &c. The 

 latter my readers will readily recognise when I tell 

 them it is the common pink or red variety usually 

 bought at Torquay, and which, when polished in 

 the mass for mantel-pieces, has such an attractive 

 appearance. All of them are portions of reef-build- 

 ing corals, and well do I remember the animated 

 appearance of the clear water when the "reefs" 

 flourished in their bright colours, and trilobites, 

 fish, and crustaceans swarmed around the busy pile. 

 The Trilobites found in the Devonian limestones 

 are of a peculiar type, equally distinct from those 

 of the preceding Silurian period, or of the succeed- 

 ing Carboniferous. 



Among the commonest of the genera were Bron- 

 tes, noted for its fan-like tail, .and Homalonotus, 

 equally distinguished by the double row of small 

 spines rnnning down the central lobe, and which 

 give to it a more " trilobed " appearance than any 

 other species in the whole family. But, clear though 

 the sea-water generally was in which these Devo- 

 nian beds were formed, every now and then shifting 

 currents brought fine mud and other sediments. 

 These were thrown down on the ocean-floor, where 

 they alternated with the bands of limestone. 



Eventually, the sea again maintained its purity 

 for a long period, during which the corals and other 

 clear-water-loving animals resumed their avocations> 

 and left behind them traces of their work. 



I have said that in Ireland there seems to have 

 been a continent, or some other extension of dry 

 land, towards the close of the age in which I was 

 born. Of this I cannot speak with certainty ; but 

 the evidence is strongly in favour of the idea. In 

 the county of Kilkenny are a series of fine-grained 

 greenish sandstpnes, regularly bedded ; they are full 

 of evidences of fresh-water deposition. Nowhere, 

 in Europe at least, will you meet with such well- 

 preserved land-plants ; all of which prove, by the 

 perfect manner in which they have been preserved, that 

 they could not have been drifted from a distance, or 

 been in the water long. Among the most attractive 

 of these remains are those of a tree-fern, formerly 

 called Cyclopteris, or "Round-leaved Eern," but now 

 named Balceopteris Hibernicus, or the " Irish Primi- 

 tive Eern." Nothing could be more exquisite than 

 this beautiful fern, even in a fossil state, and you 

 may therefore guess how attractive were its groves 



when it was the monarch of the primeval forests, 

 and its graceful fronds bent over the clear waters 

 of a lake which equalled in picturesqueness those 

 of the Emerald Island of these times. 



This fern is not unlike, in general appearance, the 

 " Royal Eern " [Osmunda regalis), with the excep- 

 tion that it has no mid-rib — its veins ramifying from 

 the base towards the exterior of the leaf. Associated 

 with this tree-fern were great and small club-mosses, 

 which trailed over the ground, and formed a rich 

 green carpet of various tints. Among the commoner 

 of these extinct club-mosses were Sagenaria (of 

 which the seed-vessels and catkins are well pre- 

 served) ; Psilophyton, a simpler club-moss, and the 

 larger and more tree-like Lepidodendron, which 

 afterwards became so abundant during the Car- 

 boniferous epoch. 



Besides these we have evidences of other kinds 

 of vegetation, aud there is no doubt that the higher 

 grounds were more or less covered with more highly- 

 developed and organized species. What is further 

 corroborative of the fresh-water origin of the Irish 

 sandstones is the immense number of bivalve shells, 

 exactly resembling the large fresh-water mussels 

 (Anodon) which abound in the English rivers. Both 

 in appearance and structure these fossil shells are 

 evidently closely allied, and therefore they are called 

 Anodonta. They abound by thousands in some 

 parts of the sandstones, associated with plant-re- 

 mains, and those of crustaceans which seem allied 

 to the modern crayfish. So long did these large 

 Irish lakes exist, that mud was strewn along their 

 bottoms, which ultimately formed rock several 

 hundred feet in thickness. I am told that similar 

 deposits of line mud and shell marl are now going on 

 along the floors of the forest-fringed lakes of North 

 America. 



Change the character of the vegetation and you 

 have no indistinct restoration of the Irish Devonian 

 lakes. Many of the fish would do ; for the "bony 

 pike," a ganoid fish, still lives there, associated 

 with colonies of " swan mussels," clustering on the 

 bottom. 



So much for the brief outlines of my story. Much 

 more could be said upon this remarkable epoch; but 

 if I have given anything like an idea of how my 

 origin was brought about, and of the character of 

 the life-forms with which I was brought into con- 

 tact, my business is done, and I accordingly retire 

 for another geological speaker. 



Helix Cartusiana.— At page 261 of your 

 Science-Gossip for November 1st, 1870, Dr. Halley 

 writcs, that lie does not know any locality where 

 this species is found. I find it in great plenty on 

 the Downs near Lewes, aud shall be most happy to 

 send duplicates to Dr. Halley if he wishes for them, 

 and would communicate with me on the subject.— 

 /. Jenner Weir, 6, Haddo Villas, Blaclihecdh, S.E. 



