446 MOLLUSCA SUB-KINGDOM VI 
Puncturella, Lowe. Shell conical, with a perforation at or in front of the post- 
median apex, behind which there is a shelf within the cavity. Eocene to Recent. 

Fic. $12. 
Rimula Goldfussi, 

Fic. 810. Fic. 811. Roemer sp. Coral-Rag : 
Emarginula Schlotheimi, Emarginula Muensteri, Pictet. Hoheneggelsen, Hanover. 
Bronn. Oligocene ; Wein- Keuper; St. Cassian, Tyrol. A, Natural size. 3B, En- 
heim, near Alzey, Baden. A, B, Natural size. C, Enlarged. larged. 
Emarginula, Lam. (Figs. 810, 811). Conical or cap-shaped, with persistent post- 
median apex, and a slit in the front margin of the shell. Surface cancellated. 
Carboniferous to Recent. 
Rimula, Defr. (Fig. 812). Like the last, but slit replaced by a closed hole on the 
anterior slope. Lias to Recent. 
Subemarginula, Blainv. Like Emarginula, but slit short or wanting, and no slit- 
band. Eocene to Recent. 
Scutus, Montf. (Parmophorus, Blainy.). Shell depressed, oblong, without fissure, 
slit, or slit-band ; muscle impression near the edge. Eocene to Recent. 
The families Phenacolepadidae, with the single genus Phenacolepas, Pils. (Scutellina, 
Gray), Cocculinidae, and Addisoniidae are recent groups allied to the Fisswrellidae. 
Family 5. Huomphalidae. de Koninck. 
Shell depressed conical to discoidal, spirally coiled, more or less deeply and widely 
umbilicate. Whorls sometimes in a loose spiral, smooth or angular; the earlier whorls 
frequently separated off by partitions. Outer lip usually with a shallow indentation. 
Operculum calcareous. Cambrian to Cretaceous. 
The Euomphalidae belong primarily to the Palaeozoic era. They have been 
variously associated with the Trochidae, Turbinidae, Littorinidae, and Solariidae. The 
shells bear a strong resemblance to those of the last-named group, but in Solariwm the 
embryonic apex is sinistral, whereas in the Huomphalidae it is dextral. Opereula are 
known with certainty in only a few genera, such as Maclurea. de Koninck surmised 
that the deeply excavated, slipper-shaped opercula from 
the Carboniferous, described originally as Calceola 
Dumontiana, are referable to Huomphalus. 
Straparollina, Billings. Cambrian. Ophileta, Van- 
uxem. Cambrian to Silurian. Maclurea, Leseueur. 
Ordovician and Silurian. 
Platyschisma, M‘Coy.  Thin-shelled, depressed 
conical, smooth. Umbilicus relatively narrow; outer 
Fic. 813. lip with broad sinus. Silurian to Carboniferous. P. 
Straparollus Dionysii, Montf. Car- helicoides, Sow. Carboniferous. 
boniferous ; Visé, Belgium. 2 ; i ; . 
Straparollus, Montf. (Fig. 813). Turbinate to dis- 
coidal, with broad umbilicus. Whorls smooth or with fine transverse striae. Silurian 
to Jura; especially abundant in Devonian and Carboniferous. 
Phanerotinus, Sow. Like the last, except that the whorls form an open spiral. 
Carboniferous. 
Euomphalus, Sow. (Plewronotus, Hall; Schizostoma, Bronn), (Fig. 814). Depressed 

