Sub Kingdom V. MOLLUSCOIDEA. 



UNDER the term Mottuscoidea, Milne-Edwards included the Bryozoa and 

 Tunicata, of which the first had been previously regarded as Zoophytes, and 

 the second as Mollusks. Huxley afterwards assigned the Brachiopoda to the 

 same phylum. These three classes form a group intermediate in position 

 between the Worms and Mollusks, and are considered by many zoologists as 

 directly related to the one or the other. The Tunicata have more recently 

 been regarded as an independent animal type, and as the probable progenitors 

 of the Vertebrates. To the palaeontologist, however, they are devoid of 

 practical interest, owing to their total lack of hard parts. 



The typical Molluscoidea either secrete a calcareous shell, or are invested 

 with a membranaceous or corneous covering. The respiratory organs lie 

 anterior to the mouth, and are in the form of tentacles or fleshy spiral 

 appendages. The m6uth conducts into a closed alimentary canal. The 

 nervous system is highly organised, and proceeds from a central ganglion, 

 situated in most cases between the mouth and the anus. Reproduction is 

 either sexual or takes place by budding. The ontogeny of the Molluscoidea 

 is most nearly comparable with that of the Annelids. 



All of the Molluscoidea are water inhabitants ; the Bryozoans are largely, 

 and the Brachiopods exclusively, marine forms. 



Class I. BRYOZOA. Ehrenberg. 1 



Small, almost always composite animals forming by gemmation variously shaped 

 colonies, each zooid of which is enclosed in a membranaceous or calcareous double- 



1 Literature : 



iVOrbigny, A., Paleontologie Frai^aise ; Terrain cretace, vol. V., 1850-51. 

 Hayenow, P., Die Bryozoen der Maestricher Kreidebilduug. Cassel, 1851. 

 Haime, J., Description des Bryozoaires fossiles de la Formation jurassique (Mem. Soc. Geol., France, 



2nd ser. vol. V.), 1854. 

 Busk, G., Catalogue of Marine Polyzoa in the Collection of the British Museum (Parts I. and II., 



Cheilostomata), 1852-54. (Part III., Cyclostomata), 1875. 

 />'">/, '/., .Monograph of the fossil Polyzoa of the Crag (Palaednt. Soc.), 1859. 

 Gabb, .W. M., and Horn, G. H., Monograph of the fossil Polyzoa of the Secondary and Tertiary 



Formations of North America (Journ. Acad. Nat. Sci. Philad., 2nd ser., vol. V.), 1862. 

 Beissd, I., Ueber die Bryozoen der Aachner Kreidebildung. Haarlem, 1865. 

 Reuss, A. E., Several important papers in Denkschr. d. Wiener Akad., vols. XXIII., XXXIV. 



1863-74 ; and Palaeontographica, vol. XX., 1872-74. 

 Manzoni, A., Several important contributions on Tertiary Bryozoans in Denkschr. d. Wiener Akad.. 



vols. XXIX., XXXI., XXXVIL, XXXVIII., 1869-78. 

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