62 AMMONACEA. 



ALCADIA. Gray ? (B. M. Syn. p. 134.) Helicinse whicli tave 

 a notch in the aperture. A distinction which it ia impossible to 

 maintain. See Helioina. 



ALCADIA. Gray. Helicina major, &c. Species with a notch, 

 PL xiv. fig. 306, 307. 



ALECTEION. Montf. Buccintjm PapiUosura, Auct. fig. 422. 



ALEPAS, Eang. A genus of Pedunculated Cirripedes, either 

 without any shell, or with a scarcely visible valve on each side 

 near the orifice. 



ALYANIA. Leach, M.S. Eisso, 1818. A very imperfectly 

 described genus, founded on a single species in the British 

 Museum collection, labelled by Leach, A. globella. - "We figure 

 the Cray fossil, A. ascaris. PL xxviii. fig. 586. 



ALVEOLINA. D'Orbigny. A genus of • microscopic Eorami- 

 nifera. 



AMALTHCEA. Schumacher, 1817. A generic name given to 

 the small flattish species of Capulus. 



AMALTHTJS. Montf. A. margaritaceus, Montf. is a species of 

 Ammonites, described aa very flat, keeled, with an angular 

 aperture. It belongs to the family Ammonacea, Lam. 



AMATHINA. Gray, Syn. 1840. PHeopsis, or Capulus tricari- 

 natus. 



AMAEULA ■ ? A genus composed of Melania Amarula, 



Auct. and similar species. 



AMBIGUJE. Lam. The fourth section of the order Conchifera 

 Dimyaria, containing the family Chamacea, fig. 153 to 155. 



AMICULA. Gray, 1842. A genus formed for the reception of 

 Chiton vestitus, the valves of which are covered by an integu- 

 ment ; so as to be almost hidden externally. PL xxiv. fig. 507. 



AMIMONUS. Montf. Conilites ungulatus, Knorr. A species 

 distinguished only by being slightly curved ; Fam. Orthocerata, 

 Lam. 



AMMONACEA. Bl. The fourth family of the order Polythala- 

 mia, BL or chambered shells, described as thin, chambered, dis- 

 coidal, convolute, symmetrical, generally compressed, with visible 



