CONULARIDA 491 
SUB-ORDER C 
a blunt median keel. Surface smooth or with fine transverse striae, rarely longitudinally 
striated or ribbed. Aperture completely closed by an operculum, the latter being semi- 
circular, triangular, or lentiform, with lateral nucleus, and concentrically striated. 
Cambrian to Permian. 
The shells belonging here are of large size, and composed of calcium carbonate. 
The posterior portion is often divided off by 
transverse septa. 
According to Holm, the typical genus Hyolithes, 
Eichwald (Theca, Sowb. ; Pugiunculus, Barr), (Fig. 
1024), is divisible into two sub-genera. One of 
these, Orthotheca, Novak, contains forms with an 
abruptly truncated anterior end; and in the 
other, Hyolithes, s. str., the margin of the flattened 
side projects somewhat above the opposite wall. 
The forms known as Cleidotheca, Centrotheca, 
Salter ; Camerotheca, Diplotheca, Matthew ; Phare- 
trella, Hall; Ceratotheca and Bactrotheca, Novak, 
fall within the synonomy of Hyolithes. This 
genus is abundantly distributed in the Cambrian, 
Ordovician, and Silurian of North America, Great 

Fic. 1024. 
Britain, Sweden, Russia, 
and Bohemia; it occurs 
sparingly also in the De- 
vonian, Carboniferous, and 
Ordovician ; 
A, B, Hyolithes elegans, Barr. 
(Btage D); Lodenice, Bohemia. Slightly 
reduced. C, H. maximus, Barr. Cambrian 
(Btage C); Mleschitz, Bohemia. Anterior 
portion restored, with operculum; viewed 
Rermi from the side, 1/5. D, Operculum (after 
ermian. Barney 
Pterotheca, Salter; 
Phragmotheca, Barrande. Silurian. Matthewia, Walcott. 
Cambrian. 
Family 4. Conulariidae. Walcott. 
Shell rectilinear, inversely conical, rect- 
angular to rhombic in cross-section, with 
usually sharp edges, acute or truncated pos- 
teriorly. Each of the transversely striated or 
ribbed lateral faces divided into longitudinal 
halves by a superficial groove, corresponding 
internally to a median ridge. Posterior 
portion of the shell divided off by septa. 
Aperture constricted by four triangular or 
linguiform incurved lobes of the anterior 
margin. Ordovician to Jura. 
Conularia, Mill. (Figs. 1025, 1026). 
This, the solitary genus, sometimes attains 
a length of 20 em., and is represented by 
about 100 species. Its maximum distribu- 
tion occurs in the Ordovician and Silurian 
of Bohemia, Normandy, England, Sweden, and North America, and in the Devonian 
of North America and Bolivia. It is rare in the Carboniferous and Permian, and 
the last surviving species occurs in the Trias and Lias. 

Fic. 1026. 
Conularia quadrisul- 

cata, Sowb. Upper 
Carboniferous Lime- 
stone ; Glasgow, Scot- 
land. Showing well- 
preserved apertural 
margins (after Ethe- 
ridge). 
Fic. 1025. 
Conularia anomala, Barr. 
Ordovician (Etage D); 
Draboy, Bohemia. 
