NAUTILIDA, oo 
AscocerRAs, Barr., 1847. 
Etym.—Ascos, a leather bottle, ceras, a horn. 
Syn.—Cryptoceras, Barr., 1846. 
Distr.—16 sp. L.and U. Silurian; Europe,Canada. A. Bohe- 
micum, Barr. (xxx, 3). 
Shell flask-shaped ; the terminal chamber not only fills the front 
of the shell, but extends down the dorsal side, nearly its whole 
length, as a deep cavity, which is embraced by the decurrent 
edges of the four or five incomplete septa; a minute siphuncle 
on the ventral side. 
GiossocERAs, Barr., 1865. 
Etym.—Glossa, a tongue, ceras, a horn. 
Distr.—2 sp. M. and U. Silurian; Anticosti; Bohemia. 
Shell like Ascoceras, but the ventral margin of the aperture 
ligulately extended and incurved. 
APHRAGMITES, Barr., 1865. 
Etym.—A, without, phragmos, a partition. 
Distr.—2 sp. U. Silurian ; Bohemia. 
Shell like Ascoceras, but the septa are deciduous. 
PHRAGMOCERAS, Brod., 1839. 
Etym.— Phragmos, a partition, and ceras, a horn. 
Syn.—Campulites, Desh. (part), 1832; Phragmolites, Conr., 
1838. 
Distr.—50 sp. Silurian to Devonian; Europe, N. America. 
Ph. ventricosum, Murch. (xxx, 4). Silurian; England. Ph. 
callistoma, Barr. (xxxi, 6). Aperture. 
Shell compressed on the sides, curved ; aperture contracted 
in the middle; last chamber large ; siphuncle dorsal, with radia- 
tions ; septa simple. 

Gyroceras, de Koninck, 1844. 
Syn.—Nautiloceras, @’Orb, 1847. Polycronites, Troost (?), 
1840. 
Distr.—40 sp. Silurian to Triassic (7); Europe, N. America. 
G. Goldfussti, Arch. (xxxi, 7). Devonian; Hifel. 
Shell planorboid, with separated whorls; septa simple, but 
little curved ; siphuncle excentric, with radiations ; last chamber 
large ; mouth but little contracted. 
Noruoceras, Barr., 1856. 
Distr.—N. Bohemicum, Barr. (xxx, 5; xxxi, 8). U. Silurian ; 
Bohemia. 
Shell nautiloid, slightly involute ; septa but little curved, not 
lobed. 
