AMERICAN PALEOZOIC CEPHALOPODS 
223 
for the annulations. A larger form was given the same name 
by Phillips-® and his illustration is here reproduced as figure 5, 
plate XXV. Lts surface had annular ridges and intervening 
waved striae. The second species described by McCoy is Cyclo- 
ceras laevigatum McCoy, represented by him as figure 3 on his 
plate 1. At the time of the original description no transverse 
striae were known. Probably the type was a cast of the interior 
of the conch, on which the surface striae leave no impress. 
Later Foord^® figured specimens of the same species in which 
transverse striae are present where the shell is preserved. His 
illustrations are reproduced herewith as figures 3A and 3B on 
plate XXVII. Possibly the surface of the shell of Orthocera 
annularis Fleming was similarly striated. 
The third species described by McCoy under Cycloceras was 
the form described by Phillips'^S in the body of his text,, as 
Orthoceras annulatum, but which in his description of plates he 
referred to Orthoceras annulare. This form possesses trans- 
verse striae in addition to the annulations, but there are no 
vertical striae or ribs. It is the only one of the three forms 
listed by McCoy in which transverse striae were known to be 
present at the time of the description of his genus Cycloceras. 
McCoy identifies this species with Orthoceras Uneolatum Phillips 
and cites the description based on the specimen represented in 
this Journal on pi. XXV, (fig. 5). 
It appears, therefore, that McCoy included in his genus Cyclo- 
ceras at least two distinct types of structure. In one, the annula- 
tions were tuberculated where crossed by longitudinal lines; in 
the other only transverse striae were present in addition to the 
annulations. The first type of structure is that indicated by his 
original description and the accompanying small figure. The 
second type of structure is that of the three species mentioned by 
McCoy in the body of his text. 
Hyatt^^ in 1883 defined Cycloceras as including transversely 
striated Palaeozoic longicones, which at some stage of their 
growth have annular costae. Subsequently in the Zittel-Eastman 
Text-book of Paleontology, he re-defined the genus as including 
annulated orthoceracones and cyrtoceracones with discontinuous 
Geology of Yorkshire, 1836, pi. 21, fig. 9. 
Garb. Ceph. Ireland, 1897, pi. 5, fig. 1. 
op. cit., p. 239, pi. 21, figs. 9, 10. 
Hyatt, A., op. cit., p. 275. 
