GENUS — CONCHODERMA. 137 



Lepas. Linnceus. Systema Naturse, 1767. 



Branta. Oken. Lehrbuch der Naturgeschichte, Th. 2, p. 362, 



1815. 

 Malacotta et Senoclita. Schumacher. Essai d'uu Nouveau Syst. 



des Habitations des Vers., 1817. 

 Otion et Cineras. Leach. Journal de Phys., vol. lxxxv, p. 67, 



July, 1817. 

 Gymnolepas. De Blainville. Diet, des Sci. Nat., Art. Mollusca, 



1824. 

 Pamina. J. E. Gray. Anuals of Philosophy, vol. x, (Second 



Series,) August, 1825.f 



Valvce '2 ad 5, minute, inter se remote : scuta bi- 

 aut tri-lobata, umbonibus in medio marginis occludentis 

 positis : carina arcuata, terminis utrinque pcene simi- 

 libus. 



Valves 2 to 5, minute, remote from each other : scuta 

 with two or three lobes, with their umbones in the 

 middle of the occludent margin : carina arched, upper 

 and lower ends nearly alike. 



Filaments seated beneath the basal articulations of the 

 first pair of cirri, and on the pedicels of four or five ante- 

 rior pairs ; mandibles, with five teeth, finely pectinated • 

 maxillae step-formed ; caudal appendages, none. 



Distribution. — Mundane, throughout the equatorial, temperate, and cold 

 seas; attached to floating objects, living or inorganic. 



The Capitulum is formed of smooth membrane, in- 

 cluding five small valves, of which the terga and carina 

 are often quite rudimentary or absent. Valves minute, 

 thin, generally more or less linear, placed far distant from 

 each other ; sometimes imperfectly calcified and covered 

 by chitine membrane, or imbedded in it. The umbones 



refers to Conchoderma, the Quarterly Part containing this genus must have 

 appeared before 1818 : Lamarck gives the year 1814 as the date of the paper 

 in question, and I have accordingly followed him. Prom a similar reference 

 by the editor, it appears that Schumachers volume appeared before the 

 number of the ' Journal de Physique' containing Leach's Paper. _ 



f Under these nine generic names, the two common species of Con- 

 choderma have received thirty-three different specific denominations, caused 

 partly by changes of nomenclature, and partly from varieties having been 

 ranked as species. 



