The inside of the upper valve is of a shining colour, approacliing 

 to golden, and that of the lower is sometimes silvery and sometimes 

 of a lighter shade of the colour of the inside of the upper valve. 



This species varies much in shape, according to circumstances. 

 Mr. G. B. Sowerby possesses one of an irregular ovate form. In- 

 deed Placunanomia, in common with other adherent genera, varies 

 much in shape, accommodating its external form to the surface to 

 which its lower valve is attached. It is remarkable also for putting 

 on the appearance of other genera or species; and this, with the ex- 

 treme closeness of the adhesion of the lower valve, has been per- 

 haps one of the causes why it has escaped the notice of zoologists. 

 Thus, Plac. Cumingii, to a casual observer, looks like one of the 

 plicated Ousters j Plac. riidis greatly resembles tlie common Oyster, 

 Ostrea edulis ; and Plac. echinata wears something of the appear- 

 ance of some of the short-spined Spondyli. — W, J. B. 



Besides the species above recorded Mr. G. B. Sowerby has kindly 

 furnished me with an odd valve of a large species from Lu^onia, 

 beautifully iridescent internally : but as it is believed that this is 

 identical with the fine shell sold by him to the British Museum, I 

 leave the description of it to the officers of that institution, in whose 

 province it is, and who are so fully capable of doing it justice. 



This genus, then, appears to be widely diffused. Mr.G. B. Sow- 

 erby has some other odd valves which may prove new. 1 possess 

 two or three specimens adhering to Spondyli from an unknown lo- 

 cality ; but they appear to be young, and, though T am inclined to 

 think that there is among them a new species, I wait for further 

 information before I venture to characterize it. — W. J, B. 



Mr. Owen read the following Notes on the Anatomy oHhe pur- 

 ple-crested Touraco, Corythaix porphyreolopha, Vig. 



"In commencing the anatomical examination of this Bird, my at- 

 tention was first directed to the form of the tongue. This was large, 

 and not confined to the posterior region of the mouth, but ex- 

 tended to the end of the lower mandible : its apex was beset with 

 a few small horny bristles directed forwards, as in the Toucans, 

 Rhamphastos, Linn., but much less produced than in those birds. 

 It is probable that the ripeness of fruit on which these birds feed is 

 tested by these yielding processes. The base of the tongue was, as 

 usual, beset with retroverted /ja;9///<^, and elevated into a distinct 

 ridge, serving, as in many of the cold-blooded ovipara, as an epi- 

 glottis. The interspace between this ridge and the laryngeal aper- 

 ture was very glandular. That aperture was simple and terminated 

 posteriorly by two retroverted spines; so that it is defended in some 

 degree against regurgitated food as well as from that which is swal- 

 lowed. 



" The oesophagus is continued down to the stomach of uniform 

 ample width (its diameter being i rds of an inch) without any dilatation 

 or ingluvies, as in the true Rasorial birds. Its termination for about 

 4ths of an inch is occupied by the zone of gastric glands, forming 

 the proventriculus, which does not deviate in capacity or course from 



