362 



NOTE ON THE GENUS FSEUDOMALAXIS, FISCHER, AND 

 DESCRIPTIONS OF A NEW SPECIES AND SUB-GENUS. 



By tli(j ^laivjiiis dc Montekosato. 



Read 13th June, 1913. 



Carefdl attention to Dr. Fischer's diagnosis of his sub-genus 

 Pseudomalaxis indicates that he did not appreciate the differences 

 separating his selected type (^Bifrontia zanclea, Phil. — a fossil) from 

 the species which is found living at Madeira. The latter is characterized 

 by the complete detachment of the whorls, a fact not mentioned by 

 Fischer, who united the two forms. 1 propose, therefore, to raise 

 Pseiidomalaxis to generic ratik (for it has no connexion with Bifro7itia, 

 fossil species from the Paris Basin ^), and to constitute a new sub-genus, 

 Spirolaxis, for the Madeiran shell. 



The European species (for I have no knowledge of the extra- 

 European forms) will stand as follows : — 



PsEUDOMALAXis, Fischcr. 

 Man. de Conch., 1885, p. 714. 

 Type, Bifrontia zanclcca^ Phil. 



1. PSEUDOMALAXIS ZANCLJiA (Pllilippi). 



Bifrontia (?) zanclcea, Phil. Enuin. ]MolI. Sicil., vol. ii, p. 225, 

 pi. xxviii, fig. 1 1. 



Fossil in the Messina district; unknown in a living state. 



2. PsECDOMALAXts Aldrovandi (Forcsti). 



Solarium Aldrovandi, Foresti, Mem. Accad. Sci. Inst. Bologna, 

 ser. II, vol. vii, pi. 625, pi. ii, figs. 17-20, 1868. 



Discuhelix {Pseudomalaxis) Aldovrandi [sic] (For.) ; Sacco, Moll. 

 Terz. Piemonte e Liguria, pt. xii, ]). 75, 1892. 



Var. Ligustica, Sacco, I.e., pi. ii, fig. 65. 



Fossil of Orciano and Zinola ; extinct. 



3. PsEUDOMALAXIS ACTONI, U.sp. 



Pseiidomalaxis, Omalaxis, and Bifrontia zanclaa, auct. 



Jlab. — Living in the coralline zone at Naples, Palermo, Algeria, 

 and Sardinia (coll. Monterosato). 



The largest species of the genus, measuring lat. 15, alt. 3 mm. 

 Very dilated, umbilicus widely open, surface roughened, ornamented 

 at the peripliery with minute denticulations. Named in honour of 

 Admiral G. Acton, one of the oldest concliologists, who was the first 

 to discover it. 



^ Bifrontia hifrons, Dcshayes. 



