Fam. 4. Radiolitidae.—Shell conical or biconvex, without canals in the external layer. Radiolites. Biradiolites.
Fam. 5. Hippuritidae.—Fixed valve long, cylindro-conical, with three longitudinal furrows which correspond internally to two pillars for support of the siphons. Hippurites. Arnaudia.
Sub-order VII.—Myacea.
Mantle closed to a considerable extent; siphons well developed; gills much folded and frequently prolonged into the branchial siphon. Foot compressed and generally byssiferous. Shell gaping, with a pallial sinus.
Fam. 1. Psammobiidae.—Siphons very long and quite separate; foot large; shell oval, elongated, ligament external. Psammobia; British. Sanguinolaria. Asaphis. Elizia. Solenotellina.
Fam. 2. Myidae.—Siphons united for the greater part of their length, and with a circlet of tentacles near their extremities; foot reduced; shell gaping; ligament internal. Mya; British. Sphenia; British. Tugonia. Platyodon. Cryptomya.
Fam. 3. Corbulidae.—Shell sub-trigonal, inequivalve; pallial sinus shallow; siphons short, united, completely retractile; foot large, pointed, often byssiferous. Corbulomya. Paramya. Erodona and Himella are fluviatile forms from South America.
Fam. 4. Lutrariidae.—Mantle extensively closed; a fourth pallial aperture behind the foot; siphons long and united; shell elongated, a spoon-shaped projection for the ligament on each valve. Lutraria; British. Tresus. Standella.
Fam. 5. Solenidae.—Elongated burrowing forms; foot cylindrical, powerful, without byssus; shell long, truncated and gaping at each end. Solenocurtus; British. Tagelus; estuarine. Ceratisolen; British. Cultellus; British. Siliqua. Solen; British. Ensis; British.
Fam. 6. Saxicavidae.—Mantle extensively closed, with a small pedal orifice; siphons long, united, covered by a chitinous sheath; gills prolonged into the branchial siphon; foot small; shell gaping. Saxicava; British. Glycimeris. Cyrtodaria.
Fam. 7. Gastrochaenidae.—Shell thin, gaping widely at the posterior end; anterior adductor much reduced; mantle extensively closed; siphons long, united. Gastrochaena; British. Fistulana.
Sub-order VIII.—Adesmacea.
Ligament wanting; shell gaping, with a styloid apophysis in the umbonal cavities. Gills prolonged into the branchial siphon. Mantle largely closed, siphons long, united. Foot short, truncated, discoid, without byssus.
Fam. 1. Pholadidae.—Shell containing all the organs; heart traversed by the rectum; two aortae. Shell with a pallial sinus; dorsal region protected by accessory plates. Pholas; British. Pholadidea; British. Jouannetia. Xylophaga; British. Martesia.
Fam. 2. Teredinidae.—Shell globular, covering only a small portion of the vermiform body; heart on ventral side of rectum; a single aorta; siphons long, united and furnished with two posterior calcareous “pallets.” Teredo; British. Xylotrya.
Sub-order IX.—Anatinacea.
Hermaphrodite, the ovaries and testes distinct, with separate apertures. Foot rather small. Mantle frequently presents a fourth orifice. External gill-plate directed dorsally and without reflected lamella. Hinge without teeth.
Fam. 1. Thracidae.—Mantle with a fourth aperture; siphons long, quite separate, completely retractile and invertible. Thracia; British. Asthenothaerus.
Fam. 2. Periplomidae.—Siphons separate, naked, completely retractile but not invertible. Periploma. Cochlodesma. Tyleria.
Fam. 3. Anatinidae.—Siphons long, united, covered by a chitinous sheath, not completely retractile. Anatina. Plectomya; Jurassic and Cretaceous.
Fam. 4. Pholadomyidae.—Mantle with fourth aperture; siphons very long, completely united, naked, incompletely retractile; foot small, with posterior appendage. Pholadomya.
Fam. 5. Arcomyidae.—Extinct; Secondary and Tertiary. Arcomya. Goniomya.
Fam. 6. Pholadellidae.—Extinct; Palaeozoic. Pholadella. Phytimya. Allorisma.
Fam. 7. Pleuromyidae.—Extinct; Secondary. Pleuromya. Gresslya. Ceromya.
Fam. 8. Pandoridae.—Shell thin, inequivalve, free; ligament internal; siphons very short. Pandora; British. Coelodon. Clidiophora.
Fam. 9. Myochamidae.—Shell very inequivalve, solid, with a pallial sinus; siphons short; foot small. Myochama. Myodora.
Fam. 10. Chamostraeidae.—A fourth pallial aperture present; pedal aperture small; siphons very short and separate; shell fixed by the right valve, irregular. Chamostraea.
Fam. 11. Clavagellidae.—Pedal aperture very small, foot rudimentary; valves continued backwards into a calcareous tube secreted by the siphons. Clavagella. Brechites (Aspergillum).
Fam. 12. Lyonsiidae.—Foot byssiferous; siphons short, invertible. Lyonsia; British. Entodesma. Mytilimeria.
Fam. 13. Verticordiidae.—Siphons short, gills papillose; foot small; shell globular. Many species abyssal. Verlicordia. Euciroa. Lyonsiella. Halicardia.
Order IV. Septibranchia
Gills have lost their respiratory function, and are transformed into a muscular septum on each side between mantle and foot. All marine, live at considerable depths, and are carnivorous.
Fam. 1. Poromyidae.—Siphons short and separate; branchial siphon with a large valve; branchial septum bears two groups of orifices on either side; hermaphrodite. Poromya; British. Dermatomya. Liopistha; Cretaceous.
Fam. 2. Cetoconchidae.—Branchial septum with three groups of orifices on each side; siphons short, separate, branchial siphon with a valve. Cetoconcha (Silenia).
Fam. 3. Cuspidariidae.—Branchial septum with four or five pairs of very narrow symmetrical orifices; siphons long, united, their extremities surrounded by tentacles; sexes separate. Cuspidaria; British.
Authorities.—T. Barrois, “Le Stylet crystallin des Lamellibranches,” Revue biol. Nord France, i. (1890); Jameson, “On the Origin of Pearls,” Proc. Zool. Soc. (London, 1902); R. H. Peck, “The Minute Structure of the Gills of Lamellibranch Mollusca,” Quart. Journ. Micr. Sci. xvii. (1877); W. G. Ridewood, “On the Structure of the Gills of the Lamellibranchia,” Phil. Trans. B. cxcv. (1903); K. Mitsukuri, “On the Structure and Significance of some aberrant forms of Lamellibranchiate Gills,” Quart. Journ. Micr. Sci. xxi. (1881); A. H. Cooke, “Molluscs,” Cambridge Natural History, vol. iii.; Paul Pelseneer, “Mollusca,” Treatise on Zoology, edited by E. Ray Lankester, pt. v.
LAMENNAIS, HUGUES FÉLICITÉ ROBERT DE (1782-1854), French priest, and philosophical and political writer, was born at Saint Malo, in Brittany, on the 19th of June 1782. He was the son of a shipowner of Saint Malo ennobled by Louis XVI. for public services, and was intended by his father to follow mercantile pursuits. He spent long hours in the library of an uncle, devouring the writings of Rousseau, Pascal and others. He thereby acquired a vast and varied, though superficial, erudition, which determined his subsequent career. Of a sickly and sensitive nature, and impressed by the horrors of the French Revolution, his mind was early seized with a morbid view of life, and this temper characterized him throughout all his changes of opinion and circumstance. He was at first inclined towards rationalistic views, but partly through the influence of his brother Jean Marie (1775-1861), partly as a result of his philosophical and historical studies, he felt belief to be indispensable to action and saw in religion the most powerful leaven of the community. He gave utterance to these convictions in the Réflexions sur l’état de l’église en France pendant le 18ième siècle et sur sa situation actuelle, published anonymously in Paris in 1808. Napoleon’s police seized the book as dangerously ideological, with its eager recommendation of religious revival and active clerical organization, but it awoke the ultramontane spirit which has since played so great a part in the politics of churches and of states.
As a rest from political strife, Lamennais devoted most of the following year to a translation, in exquisite French, of the Speculum Monachorum of Ludovicus Blosius (Louis de Blois) which he entitled Le Guide spirituel (1809). In 1811 he received the tonsure and shortly afterwards became professor of mathematics in an ecclesiastical college founded by his brother at Saint Malo. Soon after Napoleon had concluded the Concordat with Pius VII. he published, in conjunction with his brother, De la tradition de l’église sur l’institution des évêques (1814), a writing occasioned by the emperor’s nomination of Cardinal Maury to the archbishopric of Paris, in which he strongly condemned the Gallican principle which allowed bishops to be created irrespective of the pope’s sanction. He was in Paris at the first Bourbon restoration in 1814, which he hailed with satisfaction, less as a monarchist than as a strenuous apostle of religious regeneration. Dreading the Cent Jours, he escaped to London, where he obtained a meagre livelihood by giving French lessons in a school founded by the abbé Jules Carron for French émigrés;
