8 
CATALOGUE OF 
2. Anomia. Shell not eared; upper valve with three subcentral 
muscular scars ; the anterior upper lobe of the notch separated 
from the cardinal edge ; the plug entirely shelly, and quite 
free from the edge of the notch. 
3. Limanomia. Shell eared on each side of the umbo ; sinus high 
up near umbo. Muscular scars ? Fossil. 
1. PLACUN ANOMIA. 
Upper or dorsal valve with two subcentral muscular scars ; the up- 
per scar radiately veined. Byssal notch distinct, converted into 
a hole by the upper part of the anterior lobe of the notch being 
soldered to and foiming part of the cardinal edge : the plug tri- 
angular, gradually enlarging in size ; the apex and outer surface 
next to the body to which it is attached, calcareous, longitudi- 
nally striated ; the inner surface covered with horny, longitudinal, 
parallel laminae, and more or less agglutinated to the edge of the 
notch. 
Anomia, /3., Schumacher, Essai, 1817. 
Placunanomia, Broderip, Proc. Zool. Soc. 1832, 29 ; Muller, Syn. 
176; Desh.in Lamk. Hist. vii. 269; Gray, P. Z. Soc. 1849, 
119. 
Pododesmus (decipiens), Philippi, Wiegmann, Arch. i. 385, 1837. 
Anomia, pars. Bluinv. Man. Mol . ; Montague ; Forbes ^ Hanley. 
Ostrea, sp. Da Costa ; Montague. 
Placunanomia, D'Orh. Amer. Merid. 
Placunomia, Sivains. Malac. 3!), 1840. 
Mr. Broderip, who established this genus, does not observe the 
character furnished by the muscular impressions, or the lobe of the 
notch ; he merely says, “ Impressio muscularis in utraque valva 
subcentralis. In valva superiore organ! adhesionis impressio super- 
addita.” And further, that “ the organ of adhesion, which in its 
bony character (for it is more bone than shell) resembles that of 
Anomia, does not perforate the lower valve directly, but is inserted 
between the laminas of the internal surface of the lovver valve, above 
the muscular impression and below the hinge, and passes out into 
an external, irregular, somewhat longitudinal, superficial fissure or 
cicatrix, which is narrowest at the hinge margin, and which it en- 
tirely fills to a level with the surrounding surface.’’ 
This form is produced by the gradual increase of the size of the 
plug and the simultaneous increase of the size of the shell. 
Some have considered the “ plug” or “ stopper” of Anomia to be 
a third valve, which is evidently a mistake. Phillippi {Moll. Sicil. 
