190 Mr. Montacu’s Account of some new and rare 
 eighths of an inch, that of the inferior valve one inch ; breadth 
seven-eighths. 
I have great pleasure in recording this rare shell as a produc- 
tion of the British seas: three of them were taken up on the cod- 
lines in the deep, eastward of Bressay, in Zetland, by the Rev. 
Mr. Fleming, minister of that place, who favoured me with the 
specimen represented in the annexed plate. This attentive na- 
turalist assures me that the three specimens were firmly affixed 
to each other by the tube through the perforation at the beak. 
Muller appears to have described this species as an inhabitant 
of the Norwegian sea ; at least his Terebratula Cranium seems so 
nearly allied to it, that I have ventured to consider it as the same 
shell, "This great naturalist is silent with respect to the internal 
structure of the shell, or conformation of the animal. From what 
l have been able to ascertain from moistening the dried speci- 
men which came to me in its shell, it seems nearly allied to a 
Tethys, possessing but one tube or syphon, which it protrudes 
through the aperture in the beak, and which serves the triple 
purpose of mouth, foot and sucker, or instrument of adhesion. 
In the fins or margin of the animal there were several slender 
arcuated testaceous plates serving as bones, but their exact situ- 
ation and peculiar office could not be ascertained. 
It must be admitted by every Conchologist, that the Linnean 
arrangement of Anomia is defective, and the characteristic de- 
scription of the genus, as well as of the animal inhabitant, is 
vague and indefinite. | à 
With respect to the species of shells at present arranged under 
the title of Anomia, some are destitute of any perforation, some 
have an opening close to the hinge in the under valve, and others 
are perforated in the beak of the upper valve, Such an essential 
difference 
