465 



Ll-TCHI. 



L1THOPHAGID/E. 



466 



a crest. Height 3 to 5 inches. The stem is slender. Flowers very 

 small, in a lax spike, and of a greenish colour ; the lip with 2 basal 

 and 2 terminal linear lobes. It is found on turfy mountainous moors 

 in Great Britain. 



(Babington, Manual of British Botany.) 



LI-TCHI, or LEECHEE, a fruit commonly sold in the markets of 

 China, and occasionally brought to England It is the produce of the 

 Euphoria (Nephellum) Litchi of botanists, a tree belonging to the 

 natural order Sapindacece. The eatable part is a pulpy flesh, which 

 covers a stone inclosed in a hard dry tesselated prickly pericarp. The 

 Rambutan and another fruit, called the Long-yen, or Longan, are 

 yielded by species of the same genus. The Chinese cultivate many 

 varieties of each. 



LITHOCARPUS, a genus of Plants belonging to the natural order 

 Corylacea. Blume tells us that his L. Javensis is called Papau Batu, 

 or Stone-Bark, because of its hardness. [CORYLACE.E.] (Lindley, 

 Vegetable Kingdom.) 



LITHODENDRON, a generic name of some Zoophyta, proposed by 

 Goldfuss to include Caryophyllia and Oculina of Lamarck, and 

 adopted by many geological writers in a rather vague sense. De 

 Blainville rejects the term. ('Actinologie/p. 347.) The species ranked 

 by Dr. Goldfuss in the group of lAthodendra offer many diversities 

 of structure, and lie in strata of various antiquity (' Petrefacta 

 Europte '), especially in the Transition and Carboniferous Limestones. 



LITHODES. [HoMOLiDJ!.] 



LITHODOMUS. [MYTILIM:.] 



LITHOMARGE, a Mineral which occurs massive. It is spheroidal. 

 Colour white, gray, red, yellow, blue. Streak shining. Structure 

 compact Soft. Dull. Opaque. Unctuous to the touch. Adheres 

 to the tongue. Specific gravity 2'2 to 2-5. It is found in Cornwall 

 near Redruth, in Saxony, aud some other places in Europe. Friable 

 Lithomarge occurs in scaly glimmering particles, which are phos- 

 phorescent in the dark. It is found at Ehrenfriedensdorf in Saxony. 

 The analysis by Klaproth gives 



Silica 32-0 



Alumina 26'5 



Oxide of Iron 21'0 



Chloride of Sodium 1-5 



Water 17'0 



98 



LITHOPHA'GID^E, a name applicable to all Marine Conchifera, 

 AfoUutca, Radiata, &c., that penetrate stone.", masses of madrepore, 

 and other hard corals, forming therein a nidus for themselves; but 

 more particularly applied to the Conchifera. [CLAVAGELLA ; GASTRO- 

 CH3 A.] This boring however is not confined to the Conchifera ; 

 for Petricola has the power of perforating certain rocks to a limited 

 extent : nor to the Mollusca generally ; for some of the Echinidce 

 (Radiata, for instance), are known to make shallow basin-like lodge- 

 ments in the rocks whereon they dwell. The means by which these 

 animals bore hag been the subject of anxious discussion and observa- 

 tion for many years. It has been attributed to various causes. These 

 may be divided into chemical and mechanical. The chemical causes 

 ascribed are two, first, a secretion of a chemical or acid substance, by 

 which the rock bored U supposed to be dissolved, and second the 

 influence of carbonic acid hi the liquid forming the respiratory 

 currents. The first set of chemical re-agents have not been found to 

 exist, and the last will not account for boring in wood, clay, and 

 sandstone. 



The mechanical causes described are also several. The moving 

 round of the shell is one; the use of the tongue, which contains 

 siliceous particles, SB another ; whilst a third theory ascribes the boring 

 to the action of particles of sand between the shell and the rock. It 

 is not impossible that all these causes may be in operation in different 

 animals, but at present no one is regarded as the universal agent. 



In the ' History of British Mollusca,' Messrs. Forbes and Hanley 

 have given a full account of the various theories advanced, and from 

 this work we borrow the materials of the following sketch : 



" All the species of Pholas are endowed with the remarkable power 

 of perforating various substances of considerable hardness, such as 

 stone, shale, or wood ; some indifferently, some selecting one or other 

 for their habitations. They are never naturally found free. This 

 habit of boring is common to the whole tribe of which Photos is the 

 type, and is presented also by certain members of other tribes. The 

 majority of Lamellibranchiate Mollusca may be said to be borers, 

 so far as the power of burying themselves in sand, clay, mud, or gravel 

 can give them a claim to such appellation, but the boring of the Pliolas, 

 Teredo, Xyloj,haga, Pholadedea, of the Gastrocluena and its allies, and 

 of certain species of Mytilidte, appears to be effected by very different 

 means. The question how the boring Mollusca excavate their dwell- 

 ing-places has long been discussed, and is still at issue among 

 naturalists, and the name J'hola((rom <t>v\iw to bore) [?] was applied by 

 the ancients to certain shell-fish whose power of perforating the solid 

 rock attracted their notice. A shell-fish is mentioned by Athenams 

 under the name of Pholas, probably not one of the members of the 

 genus now so called, but the Lithodomus lithophagus, or Date-Shell, 

 which ia very abundant in the seas of Greece, and used by the people 

 for food, wliilut the true Pholadei are very scarce in the vEgean, and 

 not likely to have attracted popular attention. The earliest observa- 



HAT. HIST. DIV. VOr,. III. 



tions made upon the boring of Pholas were those by the celebrated 

 Re'aumur, one of the most excellent of practical naturalists. They 

 are published in the ' Memoirs of the French Academy ' for 1812. He 

 figures the Pholas Candidas in its cavity, and attempts to account for 

 its presence there. He remarks that it is always found in cavities 

 either of soft stone or clay, that these are made by the efforts of tho 

 animal itself and by means of its foot, for when it was placed by him 

 upon soft clay, it buried itself in that substance by the action of its 

 foot. He argues that they bore only in soft clay, and that their 

 presence in stone (soft stone, which he terms ' La Banche,') is owing 

 to the former being petrified around the Pholades. He shows that 

 the dimensions of the cavity in which the full-grown Pholas is found, 

 are, as compared with shell and aperture, such that the former must 

 have remained in it since it first perforated, and could not have 

 changed its habitation. He states that the young are always found 

 in clay and the old in stone, and concludes that the stone is only clay 

 petrified by means of a viscous matter derived from sea-water. It 

 need not be said now that Reaumur's observations and conclusions 

 were fallacious, but as a first step in the inquiry they had great merit. 



" Mr. John Edward Gray, in an interesting paper on the habits of 

 Molluica published by him in the 'Philosophical Transactions' for 

 1833, gives his opinion on this question. He holds that Pholades, 

 Petricola, Venerupis, and Lithodomus bore into shells and calcareous 

 rocks by dissolving them. His reasons for holding this opinion are 

 several : 1st, Because the animals of most of them are furnished 

 with a large foot more or less expanded at the end ; 2nd, because the 

 holes fit the shell in Petricola and Gastrochaina, so as to prevent 

 rotation and the use of the asperities on its surface ; 3rd, because all 

 borers are coverd with a periostracum (thin in Teredo, Pliolas, and 

 Lasca, thick hi Lithodomus), which would be rubbed off during the 

 operation of boring ; 4th, because though some borers have spiny 

 shells others have smooth ones ; 5th, because all bore into calcareous 

 substances, wood excepted, and into sandstone only when it has lain 

 a long time under the sea and become as soft as clay. These objections 

 of Mr. Gray to the mechanical theory are some good, some bad ; 

 several not consistent with a correct knowledge of the habits and 

 structure of the genera he quotes. The same naturalist, in a paper 

 on the structure of the Pholades in the first volume of the ' Zoological 

 Journal' for 1825, held an opposite view to that quoted above ; for he 

 here maintains that the Pholades bore by means of rasping. Dr. 

 Fleming's most recently expressed opinion on this subject is in favour 

 of rasping and rotatory motion. 



" Among the best memoirs on the subject of the boring molluscs ia 

 that by Mr. Osier, published in the ' Philosophical Transactions ' for 

 1826. It is entitled ' On Burrowing and Boring Marine Animals,' and 

 contains the fruit of much careful and original observation. According 

 to this gentleman, the instinct to bore is exhibited at a very early 

 stage of the animal's life. He found Pholades completely buried when 

 so minute as to be almost invisible. He regards the curved processes 

 or apophyses within the shell of Pholas as characteristic of an animal 

 which bores mechanically by employing its shell as a rasp, holding 

 that the shell is the chief instrument by means of which Pholas bores. 

 He remarks, with respect to Pholas candidus, a species whose habits 

 he observed with great care, that it is by means of the anterior and 

 lower part of the shell, which is thicker and spiny, the boring is 

 effected. He considers the peculiar arrangement of the muscles, and 

 the suppression of the ligament in this genus, as peculiarities in its 

 organisation connected with its perforating habits. Teredo, he holds, 

 bores in like manner with Pholas, and by the same means, effecting 

 the stroke during the operation by the contraction of the posterior 

 adductor muscle. 



"Tiie boring of Saxicava however Mr. Osier maintains to be 

 effected by very different means, most probably by an acid solvent. 

 Its hole is not round ; and if there are siliceous particles in the stone 

 they are left projecting into the cavity. Mr. Osier was unable never- 

 theless to detect any direct evidence of free acid, either by the test of 

 litmus paper, or by any experiments he could devise. The account 

 given by Mr. Osier of the operations of Pholas when boring is so 

 circumstantial that we quote it in his own words : 



" ' The Pholas has two methods of boring. In the first, it fixes 

 itself by the foot, and raises itself almost perpendicularly, thus 

 pressing the operative part of the shell upon the substance to which it 

 adheres. It now proceeds to execute a succession of partial rotatory 

 motions, effected by the alternate contraction of the lateral muscles, 

 employing one valve only, by turning on its side, and immediately 

 regaining the erect position. I have observed that this method is 

 almost exclusively employed by the very young animals ; aud it 

 certainly is peculiarly adapted for penetrating in a direction nearly 

 perpendicular, so that they may be completely buried in the shortest 

 possible time. It may be observed that the posterior extremities of the 

 valves are much less produced in the very minute Pholades thau they 

 afterwards become'; and thus the time required to complete a habita- 

 tion is still further diminished ; but when the Pholades have exceeded 

 two or at the most three lines in length, 1 have never observed them 

 to work in the manner I have described the altered figure of the 

 shell, and the increased weight of that part of the animal behind the 

 hinge, would prevent it from raising itself so perpendicularly as at 

 first, independent of the narrow space it occupifs. In the motions 



2 II 



