CHAMOSTREA. 373 



The shells composing this genus are peculiar to the 

 Australasian region, and are found parasitically attached 

 to the outside of other shells or to stones at considerable 

 depths. 



Species of Myochama. 



anomioides, Stutchb. Stutchburyi, A. Adams. 



Keppelliana, A. Adams. transversa, A. Adams. 



Strangei, A. Adams. 



Genus CHAMOSTREA, Roissy. 



Siphons slightly separated, very short, their orifices den- 

 ticulated. Pedal opening with a small, ventral orifice 

 behind it. 



Shell solid, inequivalve, attached by the front slope of the 

 convex dextral valve; beaks anterior, sub-spiral; inside of 

 valves somewhat pearly. Hinge with a small pointed tooth 

 in the left valve, received into a corresponding pit in the 

 right valve ; cartilage internal, with a long, curved ossicle ; 

 ligament external. Muscular impressions large and rugose, 

 the anterior very long and narrow ; pallial line simple. 



Syn. Cleidothaerus, Stutchbury. 



Ex. C. albida, Lamarck, pi. 98, fig. 4. Shell, C. albida, 

 fig. 4, a, 4, b. Ossicle, C. albida, 4, c. 



The animal of Chamostrea has been described by Han- 

 cock. The pedal opening is small, with a minute, ventral 

 orifice behind it as in Pholadomya and Myochama. The 

 mantle-lobes are united between the aperture for the foot 

 and the short, diverging, denticulated siphons ; the foot is 

 small and compressed; the lips are bi-lobed, and the dis- 

 united palpi are long and obtusely pointed. The gills are 



VOL. II. 3 c 



