526 



MOLLUSCA 



PHYLUM VI 



Of tlie three subfamilies iiito wliicli tliis group is divided, the Fissurellinae are 

 known only in tlie recent fauna. Fissurellidinae occur in the Pliocene ; all tlie 

 eai'lier forms are Emarginulinae. 



Fissurella Brug. Sliell conical, oval, witli an oval apical orifice 

 bounded inside by an entire calliis. Recent. The niimerous fossil 

 species referred to this genus belong to Fissuridea. 



Fissurellidea d'Orb. ; Pupillaea Gray ; Megatehennus and Luca- 

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

 witli the apical orifice very large. 



Lucapina Gray. Like Fissurella, but with large apical orifice 

 and finely crenate periphery. Pliocene and Recent. 



Fissuridea Swains. {Glyphis Carp. ; Fissurella auct.) (Fig. 858). 

 Sliell conical, oval, with apex in advance of the middle, giving 

 place to a Perforation which is bounded inside by a posteriorly 

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



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

 niedian apex, behind which there is a shelf within the cavity. Eocene to Recent. 

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



c 



AB 



858. 



Fissuridea italica 

 Defr. Miocene ; 



Grund, Hnngary. 



Fig. 859. 



Emarginula schlotheimi 

 Bronn. Oligocene; Wein- 

 heim, near Alzey, Baden. 



Emarginula muensteri Pictet. 

 Kei;per ; St. Cassian, Tyrol. 

 A, B, Natural size. C, Enlarged. 



Fig. 861. 



Tdmula goldfnssi (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 slope. Lias to Recent. 



Suhemarginula Blainv. Like Emarginula, but slit sliort 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 Fissurellida e. 



Family 4. Euomphalidae de Koninck. 



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

 umUlicate. Whorls sometimes in a loose spiral, smooth or angular ; the earlier whorls 

 frequently separated of hy partitions. Outer lip usually 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 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 Galceola dumontiana, are referable to Euomphalus. 



