GOMPHOCEKATID^. * 
245 
Barrande with Gom'pliocerm semiclausum^ Barr.^, and Gomplioceras 
\_Apioceras] oUa, Saemann^, in both of which species the smaller 
apertural orifice is indicated by an obscure sinus, without any inter- 
vening channel to separate the two orifices, such as is present in the 
majority of the GompJioceratidce. 
The following Silurian genera comprising the Division Ineqtjilo- 
BATEs {ante, p. 211, footnote) are not represented in the Collec- 
tion : — T rimer ocer as, Pentameroceras, Septameroceras. 
Big. 40. 
Outline of the aperture of (a) Trimcrocems, (b) Fentameroceras, and (<?) Septa- 
meroceras. a and h, after Barrande, h slightly enlarged ; c, after Hall. 
Genus TRIMEROCERAS, Hyatt I 
{Trimorion, Barrande, 1867“^.) 
Gen. Char. Shell with three lobes in the larger orifice of the 
aperture. 
Type, Trimeroceras staurostoma, Barr. sp. (fig. 40, a). 
Genus PENTAMEROCERAS, Hyatts 
{Pentamorion, Barrande, 1867^.) 
Gen. Char. Shell with five lobes in the larger orifice of the 
aperture. 
Type, Pentameroceras mirum, Barr. sp. (fig. 40, 6). 
1 PL Ixxxviii. fif. 12-15. 
^ Palgeontographica, Band iii. 1854, p. 163, pl. xix. if. 1, a, h, c. Hyatt has 
made this species the type of a new genus {Acleistoceras), the name Apioceras 
being preoccupied. 
® Proc. Boston Soc. Hat. Hist. vol. xxii. 1883, p. 278. 
^ Syst. Sil. de la Boh^me, vol. ii. pt. i. p. 265. 
