HARDWICKE'S SCIENCE-GOSSIP. 



43 



and full, whilst the list of varieties is great and 

 equally veraciously described. No earnest student 

 of muscology should be without this attractively got- 

 up little volume. The localities and physical con- 

 dition of growth are appended to each specific de- 

 scription. The work is based on Wilson's "Bryologia 

 Britannica," and Schimper's " Synopsis," and does 

 its author great credit. Mr. Hobkirk announces a 

 "Geographical Distribution of the British Mosses," 

 and recpiests collectors to forward him as complete 

 lists of their several districts as they can, as well 

 as the ranges and habits of the species. 



Plant Eccentkicities in Northamptonshire. 

 — The erratic occurrence of plants has often been 

 discussed iu Science-Gossip, and it is somewhat 

 nesitatingly I again venture to open the subject. 

 Sisymbrium Sophia in 1874 was not uncommon in 

 Northamptonshire. I observed it in some twenty 

 localities between Weedon and Thrapstone (the 

 Nene Valley), places thirfy-four miles apart, and 

 from Harleston to Towcester, thirteen miles apart, 

 in some dozen places ; in 1S73 I did not see a single 

 plant. Chenopodium hybridum iu 1873 was growing 

 plentifully by river-sides and waste places ; in 1874 

 but one specimen was found. Bidens tripartita was 

 very common by river, brook, and canal sides in 

 1S73 ; in 1874 it had entirely given place to Bidens 

 cernua, not a specimen of which could I find in 1873. 

 Are these two really distinct species, or but well- 

 markedvarieties? Cancer mmhe the biennial variety? 

 In contradistinction to the above may be mentioned 

 Geranium rotundifolium, which still grows in the 

 habitat near Brampton, mentioned in Sowerby's 

 first edition over sixty years ago, but Eryngium 

 campestre has disappeared from its Brockhall site, 

 though it has been noticed there later than pub- 

 lished records give. Any one passing through the 

 east and south of our county would miss the Harts- 

 tongue Pern, yet let him open the lid of one of the 

 old-fashioned village wells, aud he would almost 

 certainly be rewarded by seeing some luxuriant 

 fronds of the Scolopendrium growing therein. The 

 Vervain {Verbena officinalis) and Henbane ( Hyoscya- 

 mus niger), common plants round Northampton, I 

 am told, twenty years ago, have now almost entirely 

 disappeared. Lepidium draba has for the last three 

 years been growing freely on waste ground near 

 the Nene side, but improvements have this year, I 

 am afraid, disestablished it. Orchids are notori- 

 ously uncertain in their occurrence, but in 1874 1 

 visited a locality for the Bee Orchis (which I dis- 

 covered some twelve years ago, when a very young 

 boy entomologizing) aud found it still sparingly 

 growing there. — C. 67. Bruce, Northampton. 



" It is an astonishing fact that self-fertilization 

 should not have been an habitual occurrence. 

 Nature tells us, in the most emphatic manner, that 

 she abhors perpetual self-fertilization." — Darwin. 



GEOLOGY. 



Graptolites of the Arenig and Llandeilo 

 Rocks of St. David's. — A paper on the above 

 subject has been read before the Geological 

 Society, by John Hopkinson, Esq., P.G.S., and 

 Charles Lapworth, Esq., P.G.S. Commencing 

 with! a brief historical account of the discovery 

 of Graptolites in the neighbourhood of St. 

 David's, from their first discovery in the Llan- 

 deilo series in 1841, the authors proceeded to ex- 

 plain their views on the classification of the Grapto- 

 lites (Graptolithina, Bronn), which they place under 

 the order Hydroida, dividing them into two groups, 

 Rhabdophora (Allman), comprising the true siculate 

 or virgulate Graptolites, which they consider to 

 have been free organisms, and Cladophora (Hop- 

 kinson), comprising the dendroid Graptolites and 

 their allies, which were almost certainly fixed, and 

 are most nearly allied to the recent Thecaphora. 

 The distribution of the genera and species in the 

 Arenig and Llandeilo rocks of St. David's was then 

 treated of, and the different assemblages of species 

 in each of these subdivisions [were compared with 

 those of other areas. The Arenig rocks are seen to 

 contain a number of species which ally them more 

 closely to the Quebec group of Canada than to 

 any other series of rocks, all their subdivisions 

 containing Quebec species, while the Skiddaw 

 Slates, which before the discovery of Graptolites 

 in the Lower Arenig rocks of Ramsey Island 

 in 1872 were considered to be our oldest 

 Graptolite-bearing rocks, can only be correlated 

 with the Middle and Upper Arenigs of St. 

 David's. The Graptolites of the Arenig rocks of 

 Shropshire and of more distant localities were also 

 compared with those of St. David's. In the Llan- 

 deilo series of this district the Cladophora have 

 now for the first time been found, a few species, 

 with several species of Rhabdophora, occurring at 

 Abereiddy Bay, in the Lower Llandeilo, which alone 

 has been carefully worked, there being much more 

 to be done in the Middle and Upper Llandeilo, from 

 which very few species of Graptolites have as yet 

 been obtained. The paper concluded with descrip- 

 tions of all the species of Graptolites collected in 

 the Arenig and Llandeilo rocks of St. David's 

 within the last few years, of which sufficiently per- 

 fect specimens have been obtained, doubtful species 

 being referred to in an appendix. Porty-two species 

 were described, belonging to the following genera: 

 — Didymograptus, Tetragraptus, Clemagraptus 

 (gen. nov.), Dicellograptus, Climacograptus, Di" 

 plograptus, Phyllograptus, Glossograptus, and Tri- 

 gonograptus (Rhabdophora) ; Ptilograptus, Dendro- 

 graptus, Callograptus, and Dictyograptus {Clado- 

 phora). 



The Poiuier Existence of an Ixdo-Oceanic 

 Continent.— A valuable paper on this subject has 



