60 
NAUTILOIDEA. 
longitudinal folds is also marked by a more or less distinct tubercle. 
The whole shell is covered with fine, close-set, transverse undulated 
strige, which turn abruptly backward, passing over the back.” 
{U’ Archiac and de Vermuil.) 
Remarlcs. G. Eifelense differs from G. ornatum in its more rapid 
rate of increase and more numerous septa, as well as in the character 
and disposition of the ornaments of the test ; thus the transverse 
folds in G. Eif dense are more close-set and continuous than they are 
in G. ornatum. When the shell is wanting, the other characters I 
have named will suffice to distinguish the two species. 
I have referred the Cyrtoceras nautiloideum ” of Phillips to the 
present species with some doubt, the type specimen being badly 
preserved, the ornaments having been completely destroyed by 
mineralization. 
Horizon. Middle Devonian. 
Localities. British. J^’ewton Bushel, Devonshire. — Foreign. Ge- 
rolstein, Eifel ; Petigny, Belgium (?). 
Eepresented by a few imperfect specimens, including the type of 
Phillips’s “ Cyrtoceras nautiloideum.'” 
Gyroceras Cyclops^ Hall. 
1861. Gyroceras Cyclops, Hall, Descriptions of New Species of Fossils, 
&c. p. 40. 
1862. Gyroceras Cyclops, Hall, Fifteenth Heg. Rep. New York State 
Cab. Nat. Hist. p. 08. 
1876. Illustrations of Devonian Fossils: Cephalopoda, pi. liii. ff. 1-3. 
1879. Gyroceras Cyclops, Hall, Nat. Hist, of New York, Palaeont. 
vol. V. pt. ii. p. 387, pi. ci., pi. cii., pi. ciii. ff. 1, 2, pi. civ. ff. 1, 2. 
Bp. Char. “ Shell large, discoidal, regularly coiled. Spiral open, 
making about one volution and a half. The volutions are distant 
about twenty millim. ; near the aperture they are almost contiguous 
on account of the expansion of the tube. Transverse section sub- 
circular, or broadly oval, flattened on the dorsum, and obtusely sub- 
angular on the ventral side. Tube regularly enlarging from the 
apex. Apical angle about 14°. 
“Chamber of habitation small, expanding and forming a campanu- 
late aperture, which opens outward, oblique to the spiral axis of the 
tube. This feature of the direction of the aperture is inferred from 
the lines of growth and the direction of the ornamentation of the 
test. The crenulations are preserved as flne, rounded ridges and 
strige, along the internal mould of the walls of the air-chambers. 
“ Air-chambers frequent, regular, becoming numerous towards the 
apex, having a depth of ten millim. near the grand [body] chamber, 
