172 



longitudinal ridge between the prominent tubules so characteristic 

 of the European species mentioned. 



Dimensions. — Length 8-5 mm. ; breadth 4 mm. ; length of 

 aperture 2 mm. 



Form, mid Loc. — Eocene : Muddy Creek, Victoria. 



G. 9381. Three examples of the adult. Fur chased. 



Genus MUIIEX, Linnaeus. 



[Syst. Xat. ed. 10, 1758, p. 7-16.] 



Shell rounded ; spire prominent ; whorls variced, commonly 

 three on each whorl ; aperture ovate ; anterior canal much 

 prolonged, partially closed, usually spinose. 



Several of the Australian species are with difficulty allocated 

 to the known subgenera. The passages between Murex, sensu 

 stricto, Chicoreus, and Triplex are so gradual, that it is hard to 

 say where one begins and the others end, though typical species 

 of each group are easily differentiated. 



Type. — Murex haustellum, Linnaeus. 



Subgenus TRIPLEX (Humphrey), Perry. 



[Mus. Calonnianum, 1797, p. 40 ; Perry, Conchology, 1811, pis. vi., vii. (with 

 description).] 



Pteronotus, Swainson, Malacology, 1840, p. 296 {n«n J. E. Gray, 

 \i 



Shell trigonal, spire elevated; canal long, partially closed; 

 three foliaceous and typically spinose varices succeed each other 

 at regular intervals, those on the body-whorl being in alignment 

 ■with, and joined to, the corresponding varices on the preceding 

 Tphorls, thus producing the trigonal shape. 



It is impossible to distinguish Triplex from Cerostoma, Conrad, 

 in the fossil state, the principal differential characters being in 

 the operculum. 



It is not without some hesitation that the writer admits the 

 synonymity of Triplex with Pteronotus.^ Perry (see above) includes 



» E. B. Newton, Syst. List Edwards Coll. Brit. Mus. 1891, p. 149. 



