526 



MOLLUSCA 



PHYLUM VI 



Of the three subfamilies into which this group is divided, the Fissxirellinae are 

 known only in the recent fauna. Fissurellklinae occur in the Pliocene ; all the 

 earlier forms are Emarginulinue. 



Fissurella Brug. Shell conical, oval, with an oval apical orifice 

 bounded inside by an entire callus. Recent. The numerous fossil 

 species referred to this genus belong to Fissnridea. 



Fissurellidea d'Orb. ; Piqnllaea Gray ; Megatebennus and Luca- 

 ■pinella Pilsbry ; Macroschisma Swains. These are all Recent genera, 

 with the apical orifice very large. 



Luccqmia Gray. Like Fissurella, but with large apical orifice 

 and finely crenate jjeriphery. Pliocene and Recent. 



Fissuridea Swains. {Gly])his Carp. ; Fissurella auct.) (Fig. 858). 



Fio. S5S. 



Griind, Hungary. 



truncate callus. 



Fissuridea italica . „^ ^ . , . „ , 



" ^ iinsary"*' ' Sliell conical, oval, with apex in advance of the middle, giving 

 place to a perforation which is bounded inside by a posteriorly 

 Carboniferous (?) to Recent ; very abundant in the Tertiary. 

 Puncturella Lowe. Shell conical, with a perforation at or in front of the post- 

 median aitex, liehind which there is a shelf within the cavity. Eocene to Recent. 

 Emarginula Lam. (Figs. 859, 860). Conical or cap-shaped, with persistent post- 



c 



A B 



Fig. 850. 



Emarginula schlotheimi 

 Bronn. Oligocene; Wein- 

 heim, near Alzey, Baden. 



Fig. 860. 



Emarginula muensteri Pictet. 

 Keuper ; St. Cassian, Tyrol. 

 A, li. Natural size. C, Bnlaraed. 



Rimiila goldfussi (Roem). 

 Coral-Rag ; Holieneggelsen, 

 Hanover. A, Natural size. 

 B, Enlarged. 



median apex, and a slit in the front margin of the shell. Surface cancellated. 

 Carboniferous to Recent. 



Bimula Defr. (Fig. 861). Like the last, but slit replaced by a closed hole on the 

 anterior slojje. Lias to Recent. 



Suhemarginula Blainv. Like Emarginula, but slit short or wanting, and no slit- 

 band. Eocene to Recent. 



Scutiis Montf. (Parmophoriis Blainv.). Shell dej^ressed, oblong, without fissure, 

 slit, or slit-band ; miLscle impression near the edge. Eocene to Recent. 



The families Phenacolepadidae, with the single genus Phenacolepas Pils. {ScutelKna 

 Gray), Cocculinidae and Addisoniidae are recent groups allied to the Fissurellidae. 



Family 4. Euomphalidae de Koninck. 



Shell depressed conical to discoidal, spirally coiled, more or less deeply and widely 

 umhilicate. JFhorls sometimes in a loose spdral, smooth or angular ; the earlier w]iorls 

 frequently separated off by partitions. Outer lip tisually with a shallow indentation. 

 Operculum calcareous. Cambrian to Cretaceous. 



The Euomphalidae belong primarily to the Paleozoic 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 tlic Euomphalidae it is dextral. Opercula are 

 known with certainty in only a few gcmeivi, such as Maclurea. De Koninck surmised 

 that the deeply excavated, slipj)er-.sliaped opei'cula from the Carl>oniferous, described 

 originally as Gcdceola dumontiana, are referable to Euomphalus. 



