393 
anteriorly, and terminates posteriorly in one of the strong tooth-like 
prolongations mentioned above. 
The surface of the shell is marked with 13 ribs or ridges, which 
near the umbo are slight, but become stronger, well-marked, and 
prominent as they descend. The surface between the ridges is dif- 
ferent from any previously described ; it is rather opake, not polished, 
and presents somewhat the appearance of ground glass. 
This species is the giant of the family to which it belongs. Of the 
three specimens in the Collection, the largest measures rather more 
than a full inch in length, and about three-fourths of au inch in 
breadth, the other two being slightly smaller. They were sent to the 
British Museum by Sir W. Denison, Governor of Australia, who in 
a letter to Dr. Gray informs him that they were taken ‘in water- 
holes or lagoons on the plains, on the banks of the Wamoi, a river 
which discharges itself into the Darling, and ultimately by the 
Murray into the sea in South Australia.” They were collected by 
Mr. W. Birch, who in a note to the Governor says :—‘‘ My attention 
was first drawn to the Bivalves by observing them in motion, appa- 
rently in search of food; and until a specimen was obtained, I 
was under an impression, from the rapidity of their movements, 
that they were small fishes. Undeceived in this respect, I deter- 
mined to ascertain, if possible, the means by which the mollusk 
progressed. I observed that the serrated part of the shell was down- 
ward and the valves were in constant motion, and that four antennze 
were protruded from the shell, evidently for grasping food. The 
anatomical structure of the animal appeared so much at variance 
with other mollusks, that I preserved the specimens intact. I found 
by experience that if the shells are immersed in tepid water for about 
ten minutes, the animals will be sufficiently developed for minute ob- 
servation.” 
In compliance with Sir W. Denison’s request that the name of 
the collector “should be commemorated in connexion with the spe- 
cies,” I have named it Estheria birchii. 
Magnitude, 1 inch in length, ? of an inch in breadth. 
Hab. Pools of fresh water on the banks of Wamoi River, Au- 
stralia. 
Mus. Brit. 
11. Description or a New Corat (Coratiium JOHNSONI) 
rroM Mapeira. By Dr. J. E. Gray, F.R.S., V.P.Z.S., 
ETC, 
(Radiata, Pl. XVIII.) 
Mr. James Yate Johnson, the author of an admirable ‘ Guide to the 
Island of Madeira,’ and who has for years been studying the natural 
productions of that beautiful island for the purpose of preparing a 
Fauna of it, having kindly given me some specimens of Corals from 
thence, T am induced to send the following description of a very in- 
