346 MOLLUSCA SUB-KINGDOM vi 



Class I. PELEOYPODA. Goldfuss. 1 



(Lamellibranchiata, Blainville ; Conchifera, Lamarck ; Bivalvia (Bonanni), Linne ; 

 Lipocephala, Lankester.) 



Aquatic, bilaterally symmetrical, acephalous mollusks, protected by a pair of 

 valves, which are secreted by the lateral portions of the mantle, connected by 

 a ligament, and moved by the contraction of muscles attached to the inner faces of 

 the valves ; feeding by ciliary action and destitute of a radula or jaw ; breathing by 

 lateral gills ; imperfectly sensible to light and rarely provided with peripheral visual 

 organs ; possessing olfactory organs (osphradia), auditory and equilibrating organs 

 (otocysts), tactile papillae, and a nervous system composed of ganglia united by 

 nerves, but without a pedovisceral commissure ; provided with an extensile, tactile, or 

 locomotor organ (foot) ; a circulatory system containing haemolymph, and operated 

 by a single or paired cardial ventricle and two auricles ; a more or less convoluted 

 intestinal canal, with its oral and anal extremities at opposite ends of the body ; a 

 stomach; paired nephridia, connected with the pericardium, and discharging in- 

 dependently of the rectum ; reproducing without copulation, by eggs and spermatozoa ; 

 monoecious or dioecious; development external to the ovary ; the post-larval stage 

 pi'otected by a prodissoconch, and sometimes exhibiting a special nepionic stage. 



External Characters. The Shell. The embryonic Pelecypod is pro- 

 vided with a saddle-shaped, single shell gland, which secretes a pellicle of the 

 same form, upon which, at two points corresponding to the valves, calcification 

 sets in independently. These rudiments remain connected across the dorsum 



1 Literature (see also, under the head of Mollusca, pp. 344-345) : 



Wood, AS'., Monograph of the Eocene Bivalves of England (Palaeont. Soc.), 1861. 

 Zittel, K. A. von, Die Bivalven der Gosaugebilde (Denkschr. der Wiener Akad., XXV.), 1865-66. 

 Coquand, H., Monographic du genre Ostrea des terrains cretaces, 1869. 

 Barmnde, J., Systeme Silurien de la Boheme (Acephales, vols. I.-IV.), 1882. 



Bohm, G., Die Bivalven der Stramberger Schichten (Palaeont. Mittheil. Mus. Bay. Staates, II.), 1883. 

 Neumayr, M., Znr Morphologic des Bivalveuschlosses (Sitzungsber. Wiener Akad. Bd. LXXXIIL), 



1883. Ueber die Herkunft der Unioniden (id., Bd. XCVIIL), 1889. 

 White, G. A., Review of the fossil Ostreidae of North America (Ann. Report U.S. Geol. Survey, for 



1883), 1884. 



Hall, J., Geological Survey of New York, Palaeontology, vol. V., 1884-85. 

 de Koninck, L. G., Fauna du Calcaire carbonifere de la Belgique (Ann. du Mus. d'hist. nat. de 



Belgique, vol. V., pt. 5), 1886. 

 DaU, W. H., On the Hinge of the Pelecypods and its development, etc. (Am. Journ. Sci. [3], vol. 



XXXVIII.), 1889. 

 Jackson, R. T., Phylogeny of the Pelecypoda. The Aviculidae and their Allies (Mem. Boston. Soc. 



Nat. Hist, vol. IV., No. 8), 1890. 



Menegaux, A., Recherches sur la circulation des Lamellibranches marines, 1890. 

 Neumayr, M., Beitrage zu einer morphologischen Eintheiluog der Bivalven ; mit Vonvort von E. 



Suess. (Denkschr. Wiener Akad., Bd. LVIIL), 1891. 



Hyatt, A., Remarks on the Piunidae (Proc. Boston Soc. Nat. Hist., XXV.), 1892. 

 Moynier de Villepoix, R., Recherches sur la formation et 1'accroissement de la Coquille des 



Mollusques. Thesis, 1893. 

 Ulrich, E. 0., New and little known Lamellibranchiata from the Lower Silurian Rocks of Ohio, etc. 



(Rept. Geol. Surv. Ohio, vol. VII.), 1893. New and little known Lamellibranchiata of 



Minnesota (Rept. Geol. Surv. Minn., vol. III.), 1894. 



Bernard, F., Premiere note sur le developpement et la morphologic de la coquille chez les Lamelli- 

 branches (Bull. Soc. Geol. de France [3], vol. XXIII.), 1895. 

 DaU, W. H., A new Classification of the Pelecypoda (Trans. Wagner lust. Sci. Philadelphia, vol. 



III., pt. 3), 1895. Also Proc. U.S. Nat. Mus., vol. XVII., No. 1032, 1895. 

 Hyatt, A., Terminology proposed for the Description of the Shell in Pelecypoda (Proc. Am. Assoc. 



Adv. Sci. vol. XLIV.), 1895. 



