PLACUNANOMIA.— Plate I. 



In this species, the original one described by Mr. Bro- 

 derip as the type of the genus, the orifice of the lower 

 valve is restricted to an oblong fissure, and the tendon of 

 adhesion presses itself into a space between the laminse 

 of the surrounding shell. 



Species 4. (Mus. Cuming.) 

 Placunanomia Zealandica. Plac. testa suborMctdari, 



albidd, complanatd, valvd superiore radiaiim liratd, 



liris subdistantibus ; intus caritleo-virente. 

 The Zealand Placunanomia. Shell nearly orbicular, 



whitish, smooth, upper valve radiately ridged, ridges 



rather distant ; interior blue-green. 

 Aiiomia Zealandica, in Dieli'enbach's New Zealand, vol. ii. 



p. 261. 

 Hab. New Zealand. 



A semitransparent blue-green shell, radiated with tine 

 ridges, which are obsoletely scaled, and rather irregular. 



5. (Mus. Cuming.) 



Placunanomia foliata. Plac. testa subdiaphand, sub- 

 circulari, rudi, mbfoliatd ; sordide alba, intus splen- 

 dente, valvcB swperioris medio purpureo-fu-ico ; perfo- 

 ratione maxima. 



The foliated Placunanomia. Shell subdiaphanous, 

 nearly circular, rude, rather foliate ; dead-white, shin- 

 ing within, middle of the upper valve purple-brown -, 

 orifice very large. 



Brodekip, Pro. Zool. Soc. 1834, p. !J. 



Hab. Isle of Muerte, Bay of Guayaquil, West Columbia 

 (dredged up, attached to a dead Pinna, from a bottom 

 of sandy mud, at the depth of eleven fathoms). 



It is not impossible that this species may prove to be a 

 more advanced state of P. eehinata, in which the prickly 

 scales have become obsolete. It is however distinguished 

 I from that species, so far as the limited number of speci- 

 mens enabled us to judge, by a very much larger orifice. 



