MONTEROSATO : ON PSETTDOMALAXIS, FISCHER. 363 



Sub-genus Spirolaxis, n.subgen. 

 Shell discoidal ; whorls quadrangiilai', detached, solute. 

 The operculum is characterized by Fischer in his description of 



Pseudomdaxis zanclaa, ot which species, occurring only in the fossil 

 state, it is unknown. 



4. PsEUDOMALAxrs (Spirolaxis) centriffga (Monterosato). 

 Pseudomalaxis centrifuga, Monterosato, Nat. Sicil., Ann. ix, num. 7, 



p. 161, 1890 ; Boll. Soc. Mai. Ital., vol. xvii, p. 12, 1892. 

 Mention is made in the Nat. Sicil. of the quadrangular solute 

 Avhorls and of the Madeiran habitat. 

 Oinalaxis zanclea {non Phil.), H. & A. Adams, Gen. llec. Moll., 



vol. i, p. 244, pi. XXV, fig. 9 (Madeii'a). 

 A good figure showing the characteristic separation of the whorls.^ 

 Bifrontia zanclea {no7i Phil.), Watson, Journ. Linn. Soc, vol. xxvi, 



p. 275, 1897. 

 Pseudomalaxis Macandrewi, Iredale, Proc. Make. Soc, vol. ix, p. 254, 



1911 (Madeira). 



This species is mucli smaller tlian tlie others, measuring only diam. 4, 

 alt. I'Smm., and the surface is almost smooth ; but under a good lens 

 fine spiral striae are distinctly visible in well-preserved specimens. 



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