SUB-ORDER B RHIPIDOGLOSSA 45] 
flat ; base angular at periphery. Inner lip often truncated anteriorly, thickened 01 
with teeth. Silurian to Recent. 
Sub-genera:; Tectus, Montt. (Fig. 833) ; Polydonta, Schum. ; Clanculus, Montf., ete. 

Fic. 836. 

Fic. 835. 
ta, Gibbula picta, 
Pi. 834. Monodonta (Oxystele) patula, Eichw.  Mio- Gibbula Brocchii, 
Monodonta nodosa, Minst. Broechi. Miocene; Steina- cene; Wiesen, Mayer. Pliocene; 
Keuper ; St. Cassian, Tyrol. brunn, near Vienna. near Vienna. Montopoli, Tuscany. 
Monodonta, Lam. (Figs. 834, 835). Turbinate, with nearly round aperture, the 

Fic. 841. 
Solariella peregrina, 
Libassi sp. Pliocene; Or- 
ciano, Tuscany. 

Fig. 838. 
Fic. 839. Fia. 840. = = 
Calliostoma semi- Fic. 842. 
punctatum, Miinst. Calliostoma aequalis, Lewisiella conica, a’ Orb. Margarita  margaritula, 
Keuper; St. Cas- Buy. Coral-Rag ; St. sp. Middle Lias; May, Mer. Oligocene ; Weinheim, 
sian, Tyrol. 2/). Michiel, Meuse. Calvados. near Alzey, Baden. 
columella ending below in a tooth. Trias to Recent. In the sub-genera Osilinus and 
Oxystele, Phil., the tooth is wanting. 
Gibbula, Risso (Figs. 836, 837). Turbinate or low 
conic, umbilicate, and with rounded aperture. Tertiary 
and Recent. 
Calliostoma, Swains. (Ziziphinus, Gray), (Figs. 838, 
839). Conical, with peripheral keel and flattened base. 
Trias to Recent. 
Other genera are Cantharidus, Montfort ; Lewisiella, 
Stol. (Fig. 840); Chlorostoma, Swains.; Solariella, 
Wood (Fig. 841); Margarita, Leach (Fig. 842); Fra. $43. 
Danilia, Brus. (Fig. 843), ete. Most of these have a _ Danilia clathrata, Etall. sp. Coral- 
more or less extensive Tertiary history. Be ey ele 

Family 12. Umboniidae. Adams. 
Shell small, usually depressed discoidal, smooth and lustrous, or with fine spiral 
striae, and without nacreous layer. Outer lip sharp, peristome discontinuous. Umbilicus 
often concealed by a callus ; operculum horny. Silurian to Recent. 
Allied to the recent genera Umbonium, Link. (Rotella, Lam.), Isanda, Adams, 
Camitia, Gray, ete, are a number of fossil forms, such as Pyenomphalus, Lindstrom, 
from the Silurian and Devonian ; Anomphalus, Meek and Worthen, and Rotellina, de 
