150 



SCIENCE-GOSSIP. 



[July 1, 18G5. 



THE PETHERWIN BEDS. 



LEAVING Lauiiceston by tlie western road, and 

 taking our way over Windmill Hill, a pleasant 

 walk of about a mile and a half brings us to a little 

 valley, through which a stream pleasantly ripples 

 along; green fields descend to the water's edge on the 

 one side and the wooded slopes of Landrake rise on 

 the other. Crossing the water by a rustic bridge, 

 and mounting a rather hilly bit of road, by the side 

 of the wood, we turn in through a gate on the right, 

 and find ourselves in an old quarry, known as the 

 Upper, Eastern, or Landrake Quarry, and one of three 

 on the same range, which lays bare to us those pe- 

 culiarly constituted rocks known as the Petherwin 

 beds, rendered familiar to us by the labours of some 

 of our most eminent geologists. 



This quarry is a favourite retreat of ours ; many 

 happy hours have we spent in the old place, making 

 the rocks ring to the sound of our hammer — to the 

 amazement, and no doubt the amusement, of the 

 cottagers below and occasional passers-by, who 

 whisper "I wonder what he's about," and no doubt 

 put us down as an eccentric individual, who has 

 taken to stonecracking to ease his troubled mind. 



On hammering away at the shales on either side 

 of the valley, we are not long in discovering a marked 

 distinction between the two; those on the Landrake 

 side being fossiliferous, while those on theLaunceston 

 side are not so. 



Associated also with the fossiliferous shales are 

 irregular bands and nodules of limestone. Eor- 

 raerly much limestone was raised and burnt there, 

 but now the kiln is in ruins, and the place quite 

 deserted : the geologist therefore who in these latter 

 days happens to visit Landrake Quarry wall find no 

 quarryman to apply to for fossils, but must depend 

 entu'ely on his own perseverance and skilful use of 

 his hammer. The place is, however, well worth a 

 visit ; for a suite of very interesting fossils are to 

 be obtained there. Let us endeavour to give you 

 some idea of the more characteristic forms drawn 

 from our own collection. 



Among Folyzoa may be found a pretty species of 

 Fenestella ; but, as is the case with all the fossils 

 found in the shale, it is but an impression ; notwith- 

 standing, it is beautiful, its slender radiating ribs, 

 connected with transverse bars, giving it the appear- 

 ance of open netvi^ork. 



Among Adinozoa, a beautiful coral from the 

 limestone, approaching in character to the genus 

 CyatJiophyllum, being marked with deep longitudinal 

 striae. 



Among Brachiopoda, two species of Orthls, one 

 Lepta;na, and &QYQn\\.Spirifer<s. A pretty little shale 

 Spin/era {S. ungnicula) is very plentiful in some 

 portions of the limestone, while 8. disjtmcta is found 

 chiefly in the shale. 



The specimens from the shale are all more or less 

 distorted, but those from the limestone are not thus 

 affected. 



Among Concliifera, one species each of Fullastra, 

 Cyprecarclia, and Pecten. 



Among Gasteropoda, ErempJialus is a very charac- 

 teristic form ; but the fossils axe generally very im- 

 perfect. 



Among Cephalopoda, Orthoceras is rather plentiful ; 

 several species from the limestone, also two very 

 imperfect specimens of (we believe) Clymenia. 



Among Crustacea, one trilobite, which Mr. W. Salter 

 (to whom, through the kindness of Mr. Yicary, the 

 fossil was sent) pronounces to be a variety of PJiacops 

 latifrons. The specimen in our possession is very 

 perfect ; and as trilobites are not caught every day 

 in the-Petherwin beds, we will tell you how we got 

 hold of it. We remember we had sauntered out to the 

 quarry one autumn evening, and had worked away 

 for an hour or more, with but little success, having 

 bagged but a few Spirifers, when just at the bottom 

 of the great rubbish-heap we came upon a few likely- 

 looking stones, and as we carefully examined them, 

 expecting, as Mr. Macawber did, in spite of former 

 reverses, that something would eventually turn up. 

 Toour great joy, weespied, what weatonce knewmust 

 be a part of a trilobite. True, there was but a little 

 bit of his back visible, and that was slightly weather- 

 worn ; many perhaps would have passed it by ; but 

 we had been hunting for this fellow a long, long 

 time, and at last our labour was rewarded — at last 

 we could cry "Eureka!" The question now was how 

 to make the most of him — how to get him out of 

 his hiding-place — would the crab be crabbed, or 

 would he yield to our gentle persuasions, and come 

 out of his hole ? 



Tap, tap, very carefully with our hammer ; the 

 stone gives way, and his taU is set free again ; so— 

 well done, there is one side of his head with one eye 

 quite perfect, every lens beautifully preserved. And 

 nsw shall we let well alone, or risk one more blow ? 

 Hurrah, fortune favours the brave, see a perfect 

 specimen of one of the last of the Trilobites. 



The most abundant fossils, especially in the middle 

 quarry, are the Spirifera. It is worth while clam- 

 bering over a few hedges and jumping a few ditches 

 to look at this portion of the beds. Eor several feet 

 thick the rock is full of them ; there they lie im- 

 pressing one another, and you cannot split a fragment 

 of stone without getting some trace of Spirifera. 



Another curious feature connected with the Peth- 

 erwin fossils is the flattened and contorted appear- 

 ance they generally present, showing us that at 

 some period of their history they must have been 

 subjected to enormous pressure. 



So far we have visited two of the quarries ; the 

 third it will be sufficient to mention, as very little is 

 to be got there, and it is by no means at present a 



