112 
gosus, N. costatus, N. radicula, N. subarcuatulus, N. semilituus, 
N. rectus , N. spinulosus, N. legumen, and N. raphanus. But, obliged 
to observe certain limits, I shall not dwell, in this work, on those 
fossils which are so small as to be microscopic objects, except where 
it is required for the sake of particular illustration. 
In reviewing the history of these fossils, we find many instances of 
the perplexity and confusion proceeding from an endeavour to ascer- 
tain the nature of a body, which cannot be referred to any known 
recent animal, as strictly analogous. Gesner. de Figuris Lapidum, 
Cap. xiv. p. 167, and Aldrovandus, Museum Metallicum, p. J32, 
considered them as the petrified tails of crabs ; the former naming 
them Cauda cancri, s, astaci Jiuviatilis ; and the latter, Cancritce. 
But as the knowledge of fossils advanced, their resemblance to the 
alveolus of the belemnite was perceived, and they were considered by 
many as the alveoli of large belemnites, and therefore obtained the 
name of cylindrical alveoli. Some of these fossils were even consi- 
dered as part of the vertebral spine of some marine animal : an ex- 
cuse for which may be found in the particular forms possessed by 
some of these bodies. Our countryman, Lhwydd, did not make much 
progress in developing the nature of these fossils ; he was satisfied 
with naming them Alveoli ; and, of course, with considering them 
as the alveoli of large belemnites. 
Scheuchzer, although not informed of the real nature of these fossils, 
very properly separated them from the belemnites. No correct know- 
ledge, however, was obtained respecting them, until Breyn and Klein 
made them the objects of their investigations, and were led to the con- 
clusion, that they were the remains of some marine, univalve, cham- 
bered shell. This opinion was soon confirmed by the discovery, by 
Plancus, of minute recent shells on the shores of Rimini, which appeared 
to possess the characters of orthoceratites : but no recent shells of this 
genus are known, except those which have been found in the sea sand of 
different parts, and which are so minute, as to be microscopic objects. 
