"must be obtained for that group and cannot now be to preferred to the other section of which A. tumida is the type. This reasoning, according to my opinion, can only hold good in case it must be implied that Mr. C. specially confined the genus to shells having the precise character of those in his official list, or pointed out one of them as a type, or drew up his diagnosis in such a manner as to exclude A. tumida. Mr. C. made the genus in his Syn. of the Carb. Foss. of Ireland 1844. I don't say after speaking of the Spiriferæ 2. Endostonicæ, 3. Athyridæ, etc., or which then is no account of either flamen, cardinal area, or dorsal hinge. This distinguishable genus is frequently confounded with that shell usually named Terebratulæ in the older works, but is distinguished by the large spiral appendage behind.