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 Kecent. 



FIG. 810. 



Emarginula Schlotheimi, 

 Bronn. Oligocene ; Wein- 

 heim, near Alzey, Baden. 



FIG. 811. 



Emarginula Muensteri, Pictet. 

 Keuper; St. Cassian, Tyrol. 

 A, B, Natural size. C, Enlarged. 



FIG. 812. 



Rimula Goldfussi, 

 Roemer sp. Coral-Rag ; 

 Hoheneggelsen, Hanover. 

 A, Natural size. B, En- 

 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 Eecent. 



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, Blainv.). 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 Fissurellidae. 



Family 5. Euomphalidae. 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 Solarium the 

 embryonic apex is sinistral, whereas in the Euomphalidae it is dextral. Opercula 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 Euomphalus. 



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 

 lip with broad sinus. Silurian to Carboniferous. P. 

 helicoides, Sow. Carboniferous. 



Straparollus, Montf. (Fig. 813). Turbinate to dis- 

 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. (Pleuronotus, Hall; Schizostoma, Bronn), (Fig. 814). 



FIG. 813. 



Straparollus Dionysii, Montf. Car- 

 boniferous ; Vise, Belgium. 



coidal, with broad umbilicus. 



