198 



HARDWICKE'S SCIENCE-GOSSIP. 



it had simply filled up an ocean basin to that 

 depth. As we have already seen, a gradually 

 lowered sea -bed has been proved by Darwin to be 

 necessary to continuous coral growth. 



Of all the carboniferous corals the genus Zaphrentis 

 is one of the most widely distributed and generally 

 abundant. It is usually found in a very perfect 

 condition, and may often be seen in the walls in 

 limestone countries, so weathered that it stands out 

 in high relief. This coral is not only abundant 

 wherever the carboniferous limestone occurs in Great 

 Britain, but it is also distributed through the strata 



Fig 1 18.— Vertical section of Fossil 

 Coral ( K oninckophyllum ) . 



Fig. 119. — Transverse section of Fossil 

 Coral {K oninckophyllum') in part 

 showing cellular structure. 



Fig 120. — Transverse section of Lonsdalia rugosa. 



from the bottom to the top, although the smallest 

 specimens are usually found in the upper beds, and 

 the largest in the lower. The fact that it is plentifully 

 found where shale bands occur shows that it affected 

 shallow water, for shale is a muddy deposit. 



The genus Dibunophyllum (Thomson) differs from 

 Zaphrentis in the structure of its calycle or cup. This 

 coral, as well as such other genera as Rhodophyllum, 

 Koninckophyllitm, Aspidophyllum, Clisiophyllum, 

 Histiophylhim, Cyclophyllutn, is found most abun- 

 dantly in the lower strata of the Scottish carboniferous 

 limestone system. Beith, in Ayrshire, and Dunbar, 

 Haddingtonshire, are capital collecting grounds for 



all the above-mentioned fossil corals, and perhaps we 

 may add that they are in a better state of preservation 

 at Beith than anywhere else in the United Kingdom. 

 Aspidophyllum occurs in abundance in the limestone 

 of County Down, Ireland ; and in the picturesque, 

 terrace-like outcrops of the carboniferous limestone 

 strata at Blackhead, County Clare, both this and 

 several other genera of corals are plentiful. Speaking 

 of Blackhead, induces us strongly to recommend it to 

 the young naturalist, for its rare and beautiful plants 

 and ferns, as well as for its numerous and varied 

 assemblage of fossils, among which the masses of 

 sponge spicula and Radiolarians are 

 not the least interesting. 



Lonsdalia (which obtained its name 

 after the early geologist) is another 

 abundant carboniferous coral. It is 

 very common in the neighbourhood 

 of Mold, and may be extracted from 

 the walls by the roadside in wonder- 

 ful perfection. The uppermost beds 

 of the fine escarpment of limestone 

 seen at Llangollen, in North Wales, 

 also contain it in large quantities. 

 There are many species of Lonsdalia, 

 of which rugosa and floriformis are 

 perhaps the most beautiful as well as 

 the most abundant. Both show 

 structure in the clearest manner, and 

 thin sections of them, either transverse or horizontal, 

 form exquisite low-power objects for the microscope. 

 The following are among the British localities where 

 different species of Lonsdalia may be obtained : 

 Ecclefechan, Dumfriesshire, Boghead, Lesmahago, 

 Clifton (near Bristol), almost every part of Derbyshire 

 where the carboniferous limestone crops up, but par- 

 ticularly near Castleton, and in the Welsh localities 

 above mentioned. At Boghead this fossil coral may 

 be found in very large masses, all in a capital state 

 of preservation. 



A SKETCH OF THE GEOLOGY OF 

 SWANSEA AND THE NEIGHBOURHOOD. 



By Horace B. Woodward, F.G.S., of the 

 Geological Survey of England and Wales. 



[Continued frotn page 174.] 



Triassic. 



jy EUPER. — The Dolomitic Conglomerate, 

 X v. formed chiefly of pebbles and boulders of Car- 

 boniferous Limestone in a magnesian matrix, appears 

 in the neighbourhood of Kenfigand Newton Nottage. 

 Between Gwar Coch and Dan y graig, near the latter 

 village, it abuts against the Carboniferous Limestone 

 without creeping up the combs, which generally appear 



