6J1 



LUCERNARIAD.E. 



LUCINID^E. 



642 



empoth, adhering by a circular disc, above which there is a deep 

 stricture, or short peduncle ; the disc even, strengthened by an interior 

 cartilaginous lamina, which rises up the short peduncle, and forms a 

 minute hollow firm centre. The margin of the oral expansion is 

 somewhat thickened, and divided into eight equal arms, each furnished 

 with a tuft of numerous short tentacula tipped with a gland, and 

 brighter-coloured than the body. The interior ia hollowed like the 

 blossom of a flower, the square extensible mouth projecting in the 

 centre ; and in the space between the arms there is a complicated 

 structure composed apparently of two series of foliaceous processes, 

 arranged on each side of a white line, that seems to spring from the 

 sides of the mouth. 



" These processes are formed by the complicated foldings of a thin 

 membrane attached by one side in the manner of a mesentery ; there 

 are no vessels in the membrane, but some portions of it exhibit when 

 magnified a kind of net-work of irregular cells, and the outer and free 

 edge is bounded by a thread-like line. The white central line which 

 divides them is formed of small roundish bodies arranged in two or 

 three close series, and some of these ova can at times be traced along 

 the margin of the circumference to the tentacula. 



The latter are cylindrical, and terminated with a globular head, 

 which is seemingly imperforate. The stomach is a loose thin 

 plaited extensible bag, having attached to its inner surface numerous 

 filiform ctcca, that, after their removal from the body, retain 

 their irritability for a long time, and writhe themselves like a lot of 

 worms." 



Dr. Coldstream says of it: "I find the animal very hardy ; it is 

 constantly in a state of expansion, and does not contract except when 

 very rudely handled. One specimen has lived with me for three 

 weeks, although the water has not been very often changed. When 

 I first procured it, the two rows of spots running from the mouth 

 along each arm were prominent, and of a dark reddish-brown colour. 

 Since that time they have increased in size, and have become studded 

 with numerous white oval bodies which I suppose to be ova. I see 

 some of these have made their way into the web connecting the arms, 

 but I have not observed any expelled from the body." 



In his ' History of British Zoophytes,' Dr. Johnston makes the 

 following observations on the general structure and habits of these 

 curious animals : 



"The Lucernaria are of a gelatinous consistence. The skin, or 

 corium, in smooth and thickish. After covering and giving form to 

 the body it is reflected over the oral disc, and incloses within the 

 duplicature formed by this reflection the internal viscera. The body 

 is more or leas distinctly campanulate, and is prolonged inferiorly into 

 a pedicle, very variable in length, which has its bottom conformed 

 into a sucker. From this point four ligaments, probably of a mus- 

 cular nature, rise up within the peduncle, dividing at the expansion 

 of the body into eight distinct fasciculi, one proceeding to each arm. 

 These fasciculi are composed of long parallel fibres, are analogous to 

 the lamella! of the Actinirp, and like them divide the body into eight 

 equal compartments, for the inner fold of the corium is intimately 

 connected with them on both sides. The vermiform casca lie in these 

 compartments, and the ova appear also to be generated in them, but 

 whether they have an appropriate ovary is doubtful. 



" A specimen which had undergone a certain degree of putrefaction 

 and dissolution exhibited these ova forming a complete circle rouud 

 the mouth, with rows running up the arms to the base of the tentacula. 

 The ova were proportionably large, roundish, or oval, and irregularly 

 grouped. The change produced in the appearance of the tentacula 

 was considerable, for the globular apex had disappeared, and all had 

 assumed a linear or conical figure, the centre filled with an opaque 

 granular matter forming a dark speck at the apex, and covered with 

 a clear mucous skin. The vesicle presented precisely the same 

 structure, but no aperture was visible in either part. 



" The Lucernaria can swim with some rapidity in the water by 

 alternate dilatations and contractions of the body, but they are usually 

 found adherent to sea-weeds, the first species in a dependent position, 

 the two latter invariably erect, so that Lamarck is in error when he 

 describes the mouth as behig inferior. When in a state of expansion 

 few marine worms exceed them in beauty and singularity of form ; 

 when contracted they are shapeless, and easily overlooked. They 

 feed on small crustaceous animals brought within reach by the tide, 

 and to arrest them more certainly the tentacula are widely displayed ; 

 but no sooner have they felt the prey than they instantly contract, 

 envelope it in their joint, embrace, and carry it. to the mouth by an 

 involution of the whole marginal circumference. I have found that 

 the glands with which the tentacula are tipped perform the office of 

 suckers, as Lamarck conjectured, and thus retain their captives with 

 greater certainty." 



Mr R. Q. Couch says, " Their mode of progression differs under 

 different circumstances. If intending to move to any great distance, 

 they do so by loosening their attachments, and then by various and 

 active contortions they waft themselves away, till they meet with an 

 obstruction where they rest ; and if the situation suits them, they fix 

 themselves- if not, they move on in the same manner to some other 

 spot. If the change be only for a short distance, as from one part of 

 the leaf to the other, they bend their campanulate rims, and bring 

 the tentacula in contact with the fucus, and by them adhere to it. 



The foot-stalk ia then loosened and thrown forward, and twirled about 

 till it meets with a place to suit it ; it is then fixed and the tentacula 

 are loosened, and in this way they move from one spot to another. 

 Sometimes they move like the Actinia, by a gliding motion of the 

 stalk. In taking their prey they remain fixed with their tentacula 

 expanded, and if any minute substance comes in contact with any of 

 the tufts, that tuft contracts, and is turned to the mouth, while the 

 others remain expanded watching for prey." 



LUCINA. [LUCINIDJS.] 



LUCINID^E, a family of Conchiferous Molltisca. The species 

 have a -free-closed orbicular shell; hinge-teeth 1 or 2, laterals 1-1, or 

 obsolete ; Anterior dull, obliquely furrowed ; pallial line simple ; 

 muscular impressions 2, elongated, rugose ; ligament inconspicuous, 

 or sub-internal. The animal has mantle-lobes open below, with one 

 or two siphonal orifices behind; the foot elongated, cylindrical, or 

 strap-shaped, protruded at the base of the shell; gills one (or 

 two) on each side, large and thick, oval ; mouth and palpi usually 

 minute. 



The animals belonging to this family are distributed chiefly in 

 tropical and temperate seas. They live in sand or mud, and arc 

 found from the shallowest parts of the sea to the lowest depths at 

 which life can inhabit its abysses. Woodward, in his treatise on 

 'Shells,' includes the following genera in this family : Lucina, 

 Corbis, Tancredia, Diplodonta, Ungulina, Kettia, Montacuta, Lepton, 

 and Galeonura. The four last genera are referred by some authors 

 to the family Kettiadai (Forbes and Hanley). [KELLIAD.E.] 



Lucina has the following characters : 



Shell suborbicular, inequilateral, with email pointed oblique urn- 

 bones. Two divergent cardinal teeth, one bifid, and which are variable 

 or disappear with age. Two lateral teeth; the posterior one more 

 approximated to the cardinal teeth. Two yery separate muscular 

 impressions, the posterior of which forms a facial prolongation, which 

 is sometimes very long. 



M. Deshayes observes, that the genus Lucina, as Lamarck and 

 Bruguieres perceived, is very natural ; the shells have a particular 

 contour (facies) ; they are obicular, the interior surface of the valves is 

 punctuated or striated, sometimes deeply ; the pallial impression is 

 always simple, which is an essential character of the genus, as well 

 as the form and position of the muscular impressions. When the 

 genus is studied by means of a great number of species, one soon 

 perceives that the hinge varies much, and that the characters afforded 

 by this part in other groups are here but of small value. Some 

 species have the hinge toothless, others have one or two cardinal teeth, 

 at first obsolete or rudimentary, afterwards larger and more constant. 

 To these cardinal teeth are added, according to the species, the anterior 

 or posterior lateral tooth ; and the hinge is not complete, that is to 

 say, is not provided with cardinal and lateral teeth, except in a small 

 number of species. Notwithstanding these continual variations of 

 the hinge, one may perceive that the 86 species, both recent and 

 fossil, actually known, bear so natural a relation to each other, that 

 they could not be better placed elsewhere, neither could they con- 

 stitute other genera. Some zoologists, after the example of Cuvier, 

 retain the genera Lucina of Bruguieres and Loripes of Poli. But M. 

 Deshayes observes, that though the animals of the principal Lvjncc 

 are not known, one may conclude by analogy and from the resemblance 

 of the shells, that the identity of the two genera cannot be well con- 

 tested. He therefore thinks that, as it is not convenient to retain both 

 genera, and as that of Bruguieres is best known and as old as Poli's, 

 Bruguieres's name should be preferred. 



Linnicus placed the greater part of the Lucince among his Veneres. 

 In separating these genera, Brugui&res, Lamarck, and the other 

 couchologists left among the Venerea some shells which have all the 

 characters of the Lucina;. 



The number of species recorded by M. Deshayes in his ' Tables ' is 20 

 recent and 59 fossil (tertiary) : of these L. tigrina, L. punctata, L. 

 columbella, L. divaricata, L. lactea, L. gibbosula, L. sqwamosa, L, radula, 

 and L. amphidesmoldei are noticed as recent nnd fossil (tertiary). 



Mr. Lea adds six species from the tertiary of Alabama. 



In a recent state Lucina has been found at depths varying from 5 

 to 11 fathoms in sandy-mud and mud. Species occur principally in 

 the seas of warm climates. 



Woodward gives 70 recent species and 200 fossil, and the locality 

 the Upper Silurian Rocks. 



The following species are British : L. borealis, L. spinifera, L. 

 divaricata, L. flexuosa, L, leucoma, L. ferruginosa. 



C'orbw has an oval ventricose subequilateral shell, with concentrically 

 sculptured margins, denticulated within ; hinge-teeth 2, laterals 2, in 

 each valve ; pallial line single, umbonal area with an oblique furrow ; 

 muscular impressions round and polished ; pedal scars close to 

 adductors. The animal has the mantle open below, doubly fringed ; 

 foot long, pointed; siphonal opening single, with a long retractile 

 tubular valve ; lips narrow ; palpi rudimentary ; gills single on each 

 side, thick, quadrangular, plaited, united behind. There are two 

 recent species inhabiting the seas of China, India, Australia, and the 

 Pacific. There are 80 fossil species chiefly in the Lias. 



Diplodonta, has a smooth suborbicular shell ; a double rather long 

 submarginal ligament ; hinge-teeth 2 2, of which the anterior in the 

 left valve and posterior in the right are bifid ; muscular impressions 



