UMAX. 



LIMESTONE. 



410 



with regard to temperature, and when we remark that thoso modifi- 

 cation* are capable of (Ming reduced to constant lawn, we may beliove 

 that modifying asjsauies which have acted with to much power on 

 certain races hare had an equal effect on othen ; and we may foreaee, 

 by an induction not at all forced, the future rmulu of observation ou 

 this subject If we etc, in fact, species of Htlictt modified we may 

 believe that aimilar modification* hare taken place in the Linacn. 

 These modifications are doubtless let* easily recognised in the last- 

 BMotiooed genus ; for there U no solid ahell by means of which they 

 may be traced. In this state of things M. Deshayee is of opinion that 

 the only means which science offers for the distinction of the different 

 spidss of Limojc coming from the warm and cold regions of Europe 

 are to be found in a minute dissection. A comparison resting on the 

 form and disposition of certain internal organs would lead, he doubts 

 not, to satisfactory results. Curier, continues M. Deshayes, in his 

 ssMhinslosl memoir on the Hiiictt and Limacri, has demonstrated all 

 which exists between these two genera. Thus those 



_ whose habits of obserration enable them to discover the 

 ordinary march of nature might expect to see filled up the consider- 

 able interval, in reference to the shell, which would seem to exist 

 beimm the two genera. The Marine Molluscs have already offered, 

 if not in the same family, at least in the same group, a. phenomenon 

 safficienUv similar to that which is exhibited among the Limaca and 

 HtUem. In many of the species of Umax we find no trace of a shell ; 

 in others some calcareous grains are observed in a sac included in the 

 thickness of the buckler, placed above the heart and bronchia. These 

 grain* agglutinated constitute in a considerable number of species a 

 fat calcareous plate, entirely internal ; soon we find this plate coming 

 out and showing some of its parts externally, while the remainder is 

 till embedded in the thickness of the mantle, but its free extremity 

 begin* to be twisted spirally. This sub-internal shell, quite incapable 

 of containing the least part of the animal, increases gradually, changes 

 its place when the organ of respiration changes its situation, and 

 finishes by possessing by very insensible degrees a development suffi- 

 ciently considerable to contain the entire animal, as in certain Vitrina; 

 and in all the Jldica. Of the different degrees which exist between 

 these two extremes of the series of these different modifications 

 oologist* have made so many genera. 



X. Deshayes concludes his observations by remarking that the 

 history of the Limaeet is at the present day become very considerable, 

 sod be finds it impossible to exhibit a complete view of it ; for even 

 the greatest brevity would lead htm to overstep the limits which he 

 necessarily imposed on himself in editing the work from which we 

 have quoted. He refers the reader particularly to the memoirs of 

 Cuvier for the anatomical part, and to the great work of De Fdrusaac 

 for the history of the genus, the distinction of the species, and the 

 discussion of their character*. 



The reader will find parts of the organisation of gome of the 

 Limaett in the Museum of the Royal College of Surgeons. Numbers 

 2S97 to 2802 (Gallery), both inclusive, exhibit the generative system 

 Of the Slugs. Numbers 2303 to 2311, both inclusive, illustrate the 

 same system in the Snails (Helix). No. 2315 is a specimen of 

 the spiculum amoris or calcareous dart of a Snail ; and Numbers 

 4 to 2849, both inclusive, are illustrative of the coitus in J/eli.>- 



Parmaatta. Animal elongated, oblong, demi-cylindricol, covered 

 00 the middle of the back by a rounded oblong fleshy cuirass, which 

 U to a great extent free in front ; head sufficiently distinct, carrying 

 two psirs of retractile tentacles, the one superior, long and oculiferoue, 

 the other anterior and short; foot large and oblong; respiratory 

 cavity under the posterior part of the cuirass, opening, us well as the 

 anus, by a common solution of continuity under its right border, a 

 little backwards ; orifice of generation single, near the right tentacle. 



Shell flattened, calcareous, with a membranous epidermis, oval, 

 slightly bent in the direction of its width, with a summit marked by 

 a deep sinus ou the right side posteriorly, placed in the thickness of 

 the cuirass, above the respiratory cavity. Cuvier remarks that the 

 sheU exhibit* behind a slight commencement of a spire. 



De BUaville divides the genus into two sections : the first consisting 

 of .pecies whose tail is not carinated and whose shell is subspiral 

 (example, P. Tatuta.ti and P. PaUioltm.DtTtr.); the second species 

 Which in more depressed, the tail oarinated, and the shell soutiform 

 (example, /'. fHiritri.) 



Ds HUinviU. CMalacologie') observes that only two species are 

 known, on. from Sooth America, the other from Persia. Cnvier, in 

 his ' Keen. Animal,' notices the species first known, P Olivitri, and 

 an that there U another from Bra.il (P. Pall.olw*, De F5r.), and some 

 oders from the Indies, meaning probably the East Indies. M. Rang, 

 who remarks that the PanuuxUn form a very natural genus, very 

 elotely approximating to the Slug*, stats* that in Brazil they inhabit 

 the woods, but that at Bourbon and Madagascar he never found them 

 except anon rocks near fresh-water torrent*. He adds that Olivier 

 brought the Brat specimen from Mesopotamia, and that it was this 

 Which served for the anatomical researches of Cuvier, under the name 

 of P. Wtrirrt; that I)e Porussac has described another under the 

 name of P. PmttMmm; and that he (M. Rang) brought back from 

 his voyage in the Indian Seas two others, one of which, P. Ran- 

 gia*t, has been described by M. De Fcrussac as an Arion ('Bull des 



Sciences,' February 1827); this was from the Isle of Bourbon and 

 Madagascar. 



/'. (Mirieri may be taken as an example. It U a native of Meso- 

 potamia. 



Olicitr 



M. Deshayes (2nd ed. Lam., tome viL, 1836) does not add to tho 

 single species given by Lamarck, namely, P. Oiivieri, Cuvier, (P. Meto- 

 potamia, Oken) ; but he states that an animal coming from Brazil hod 

 been sent to M. De Fc'russac, and anatomised by M. De Blainville ; 

 and had been assigned by those authors to the genus Parmacella. 

 This animal, according to M. Deshayes, offers nevertheless remarkable 

 differences in the disposition of the organs of generation ; but ho 

 thinks that these characters do not appear sufficient for the establish- 

 ment of a genus. Since then, he adds, Messrs. Webb and Bertholet, 

 who have explored the Canaries with such scrupulous attention, have 

 observed there a mollusc closely approaching tho Parmacdltr, and 

 especially that from Brazil, and in their synoptic Prodromu* (' Ann. 

 des Sci. Nat,' March 1833) they hare proposed to establish for it 

 a genus under the name of Cryptrlla ; but M. Deshayes states that 

 he waits for the description and figure before he pronounces on its 

 admission or rejection. 



The little fish the Lancelot was at first referred to the genus Limax. 

 [BRANCHIOSTOMA.] 



LIMBILITE, a Mineral so called by Saussure, which occurs in the 

 volcanic hill of Limburg. It is found in irregular grains. Structure 

 compact. Hardness 6'0 to V'O. Scratches glass easily. Colour 

 honey-yellow. Melts into a black enamel 



LIME, one of the Earths, an oxide of a metal called Calcium. It 

 combines with various acids, forming conspicuous materials of the 

 earth's surface. \JTith the exception of nitrate of lime, none of the 

 native salts of lime ore soluble except in minute proportions. They 

 give no odour and no metallic re-action before the blow-pipe. The 

 principal native salts are Sulphate of Lime [Qn-susi; ANHYDRITE], 

 Carbonate of Lime [CALCAREOUS SPAR; AURAOONITE], Magnesian 

 Carbonate of Lime [DOLOMITE], Phosphate of Lime [APATITE], and 

 Fluoride of Calcium, or Fluate of Lime [FLUOR-SPAR], 



In addition to these the following salts of lime have been 

 observed : 



Oj-alatc of Lime. It occurs crystallised. Its primary form an 

 oblique rhombic prism, and from one-tenth to one-fourth of an incli 

 long.' Colourless. Fracture conchoidal. Hardness rather less than 

 calcspar. Very brittle. Lustre similar to that of sulphate of lead. 

 Transparent to opaque. Specific gravity 1'833. Supposed to have 

 come from Hungary. Its analysis, by Sandell, showed its composition 

 to be oxalate of lime with one equivalent of water. 



J/ayaitie, or Hydrous borate of Lime, found in South America. 



Ilydroboracite, a Hydrous borate of Lime and Magnesia. 



Nitratt of Lime, found in the form of a white delicate efflorescence. 

 It occurs iu caverns in many parts of the world, and is used for the 

 manufncture of gunpowder. 



LIME. [CrtKOs.1 



LIMK, OXALATE OF. [LIME.] 



LIMKTHKK. [TII.IA.] 



LIMESTONE. This term is applied to a great variety of earthy 

 compounds, in which carbonate of lime is the predominant ingredient. 

 The chemical, molecular, and structural characters of limestone are 

 extremely interesting to mineralogy, and deserve from geologists a 

 greater share of attention than has usually been given to them. In 

 regard to the chemical composition of limestones, we may notice that 

 some, as statuary marble, are nearly pure carbonate of lime ; others, 

 as the dolomitic rocks of the Alps, contain a certain proportion of 

 carbonate of magnesia ; and some are penetrated by bituminous 

 matter, as the black marbles of Yorkshire. Limestones also vary iu 

 quality, aud become debased by admixture with sand, clay, oxide of 

 iron, pyrites, 4c. ; so that there is in fact a real gradation from lime- 

 stone to schist, to sandstone, to shale, to ironstone, &c. Limestones 

 have a crystalline aggregation, as statuary marble, and generally the 

 limestones mixed with primary systems of strata ; or they are com- 

 posed of small crystalline grains, as the magnesian limestone of 

 Mansfield in Nottinghamshire ; full of round concretionary parts, as 

 the oolites of Portland, Bath, and Oxford ; earthy, as chalk and some 

 magnesian limestones ; or compact, as the lithographic stone of 

 Solenhofen. The limestone rocks of Building Hill, Sunderland, 

 r. scmblc a coral reef. The beds of calcareous rocks are of every 

 thickness, from a mere lamina to some yards thick ; they are traversed 

 by divisional planes more or less regular, and very thick beds assume 



