SUB-ORDER B 



RHIPIDOfJLOSSA 



Family 1. Haliotidae. Fleming. 



Shell flattened, auriform, with wide aperture, and no operculum. Interior nacreous, 

 a row of perforations on the left outer margin. Marine. Cretaceous to Recent. 



Haliotis, Linn. This, the solitary genus, occurs very rarely !'<> il rxivpt in tli-- 

 Quaternary. . 



Family 2, Pleurotomariidae. d'Orbigny. 



Shell spiral, sub-spherical, turbinate, conic, turreted, or planorboid, nacreous inter- 

 nally. Outer lip with a slit, from which a slit-band (the anal fasciole) extends bd> 

 traversing all the whorls. The slit sometimes replaced by one or more perforations. 

 Operculum horny. Cambrian to Recent. 



Eaphistoma, Hall. Spire depressed or completely flattened ; whorls angular 

 above. Umbilicus moderately broad ; 

 outer lip with short notch on the keel. 

 Cambrian to Silurian. 



Pleurotomaria, 

 Defr. (Figs. 798- 

 802). Shell 

 broadly conical or 

 turbinate ; spire 



FIG. 798. 

 Pleurotomaria (Rhaphisto- 



Pleurotomaria 

 Lias ; Goppingen, 



FIG. 79P. 



i in) polita, Goldf. 

 nrtemberg. 



Lower 



Sometimes high, 



in other cases de- 



pressed ; umbili- 



cus present or absent. Outer lip with slit ; growth-lines strongly recurved, meeting 



in the slit-band. Silurian to Recent. Four living and several hundred fossil species 



known. Rare in the late Tertiary 



Sub-genera : Ptydiomphalus, Agassiz ; Mourlonia, Worthenia, Agnesia, de Koninck ; 

 Gosseletina, Ivania (Baylea, de Kon.), Bayle ; Ecqyhistomella (Fig. 798), Zij'jit'*. Lnl,ll,i. 



Fio. 800. 



Pleurotomaria Iritorquata, Des- 

 longchainps. Middle Lias ; May, 

 Calvados. 



rieurotomfirin 

 Lower Oolite ; Bayeux, Calvados. 1/2- 



Stuorella, Schizodiscus, Kittl ; Brilonella, Kayser ; Hesperiella, Holzapfel ; Cnjptnenia (Fig. 

 799), Leptomaria, Deslongchamps (Fig. 802), etc. 



Porcellia, Leveill^ (Leveilleia, Newton), (Fig. 803). Shell discoidal, Hat, widely 

 umbilicate, nearly symmetrical, and all but the first few whorls coiled in the same 



