SCIENCE-(JOSS/r. 



4' 



l'°»r ihv I'rvncl) .tpecius consult, though lliu 

 iiiiincnchitiiri- is old, Hokack Bencdk r Ai.fkkii 

 Miii.m'in-TaMion's tlisloire Nalnielle dti Molliis- 

 i/Uis lie Frana. 2 vols., with 54 phitcs, pul>lishc<i 

 1S55. Cost, aliout jtJs. with plain, and 62s. with 

 coloured plates. 



D0MIM1.HTK 1)ii'UY'.s Hisloire NaluielU dt$ 

 Molliisiiiies temslres el (Ceaii doiue qui I'ivaiil ,11 

 /■'raiui, with litho|;raphic plates hy iM. J. Dflaruc, 

 1847-52, about £1 7s. 6(1. sccond-hanil. 



For classification of shells generally, Sami'EI. 

 I'ECKWORTll WiioiiuAKli's Manual of Ihc A/ollKua, 

 (Recent and l''o.s.sil Shells), with .\ppcndix hy K. 

 Tatk, 4th edition, 2j plates, 1S90, is the best at low 

 price. It costs 7s. 6d. The great works by Kiscmhk, 

 Tkvon and Kbrhssai; are founded on this Manual. 

 I'ischer su[x;rseded Woodward, and Tr\dn and 

 I'ilsbry have again superseded Kischer. 



In French, is Tai;!. Kisrur^k's .Manuel Uc Conehy- 

 lioloi^'ie, recent and fossil, with the Brachiopods, liy 

 I>. r. Ci;iii.i:rt, pul)lishe<l in 1SS7, with 23 plates of 

 600 figures. 



Kkri'ssac ani> I)i;shavks' Hisloire Xalurelle ile 

 Motliise, 2 vols, and 247 plates, 18291857, pvd)lisliecl 

 at about ;^24 plain plates, and ^^50 with coloured 

 obtainable secondhand at £1^ los. and ^"24 respec. 

 tively. 



The most modern general work on shells was 

 founded by the late Gkori;i-; Wasiiixi-.ton Trvox 

 inider the title of a Manual of Comholog)-. It is 



^lill in proicss of publiciitlon, lx!ii)g continued by 

 IIknrv a. I'ii.shrv. The first series include.s the 

 Marine (ia-stropods in 14 volumes. The sucumi 

 scries has 8 volumes compleleil, which deal with the 

 I'ulmonata; with a special monograph of the gre-at 

 lamily Ilelicidae. It is issued in parts, with 16 to 24 

 plates in each, by the .Academy of Sciences o 

 Philadelphia. Kach volume consists of four (xirLs. 

 I'rice ifj per part, with plain plates, and 85 coloured. 



For the general natural history, classification and 

 other subjects connected with Mollu.sca, the most 

 recent work of importance in KnglLsh, is vol. 3 of the 

 Caiiihnd,^e Nalural History series. It is by A. M. 

 CooKK, A. C. Smi'i.KV, and F. R. C. RtiAU, 

 published in 1896, price 17s. net. Thi.s is one of the 

 first books which should be obtained by the beginner 

 on Mollusca. 



Reference should be made lo the back volumes of 

 the y.oologieal Rceord, ami also to that work as it 

 appears, for the latest information about mollu,sca, 

 especially w ith regard to classification. The Zootof^eal 

 Keeord is published by the Zoological Society of 

 London, the price being C\ lOs. per annual volume, 

 l-'.arly volumes can be had for about los. 6d. 



There are three English Magazines that devote 

 space to the Mollusca. They are the Journal of 

 Coneliology, the Journal of A/alacolog}', both issued 

 (|uarlerly, at 6s. per annum, and .SciKNCK-GosslI', 

 monthly, .Sixpence. 



A HISTORY OF CHALK. 



Bv 1-jiUAKii A. Mari'in, F.G.S. 

 (Continued from f>age 14.) 



C I'ECI.MKNS of Chalk taken from deep borings 

 *^ have been microscopically examined, and from 

 these, interesting results have been obtained. At 

 Culford, in Sufi'olk, Chalk brought from a depth 

 of 636ft., was found to contain foraminifers 

 amongst sheM-dust, which seemed to form the 

 matrix. In this case most of them were identi- 

 fied by Dr. G. \. Hinde as Textulariae. .-Vt 

 Ware, in Hertfordshire, a piece of soft white 

 Chalk was brought up from a depth of about 149ft., 

 and this was found by Mr. W. Hill to contain also 

 many minute Textulariae, whilst a fragment from a 

 depth of 3S7ft. contained various Glohigeriiia. which 

 was the most common genus represented. It is 

 always the same. Wherever a piece of Chalk is 

 microscopically examined, remains of Foraiiiiiii/'eraaje 

 found, whether it be newly hewn from the chalk-pit, 

 or brought up by the boring-tool from some deep 

 bore-hole. 



It was formerly ver)- widely thought that the 

 foraminifers which make up the greater part, not only 

 of the Chalk, but also of other geological formations, 

 lived at the bottom of an ocean. This erroneous 

 impression was, however, dispelled by discoveries 



which were made by the well-known "Challenger" 

 expedition. It wa.s found that these rhizopods lived 

 in countless numbers at the surface of the sea, 

 especially in the warmer waters of the tropics, and the 

 North Atlantic. They sink from the surface, after 

 death, perhaps through a mile, two miles, or nearly 

 three miles of water, as a perpetual "drizzle," 

 becoming deposited upon the bottom of the ocean in 

 the form of conglomerated chalky mud. 



The "Challenger" expedition was fruitful in its 

 results, especially in so far as it enabled geologists to 

 realise how strata were deposited — grew, so to speak, 

 at these remote depths. It will be as well here to 

 give a short account of some of the facts brought to 

 light which touch specially the subject we now have 

 under consideration. The expedition was equipped 

 by the British Government with the intentions as 

 stated by Mr. John Murray, F. R.S. E., a member 

 of the scientific stafi", which accompanied the 

 vessel. They were: — "To deleniiine, whenever 

 possible, tlie depth of the ocean. To ascertain the 

 nature of the deposits taking place over the floor of 

 the ocean. To procure specimens of sea water from 

 various levels from the surface to the bottom, and 



C3 



