70 



which vmderlay Marine Eocene, it is impossible to say. The 

 succeeding 182 ft. of sandy and clayey beds, though unfossilifer- 

 ous, have so much the character of the overlying strata with 

 marine shells that they may be reasonably regarded as forming 

 part of the same series. The chief fossiliferous beds range 

 between 90 and 150 ft., but in the midst of them, at about 

 130 ft., is a band of calcareous silt charged with Plecotrema 

 ciliatum in an excellent state of preservation. This pulmoniferous 

 mollusc is living at extreme high tide-mark in tlie marine 

 marshes abutting on the Port Creek, whilst the fine calcareous 

 silt is analogous to the shell-travertine which delimits the 

 margin of an upraised Pleistocene sea-bed, extending from Glenelg 

 via Dry Creek to beyond Virginia. This ancient silt with 

 Plecotrema must, therefore, at the period of its accumulation 

 have been at the line of junction of sea and land, and is indicative 

 of an actual depression of 130 ft. below high water-mark. The 

 associated beds, from 30 to 150 ft. in depth, are, from their con- 

 tained organic remains, shoreline accumulations, and the total 

 amount of depression evidenced thereby is a few feet less than 

 150 ft. below high water-mark. 



DESCRIPTIONS OF NEW SPECIES. 

 Odontostomia Jonesiana, Tate, 1898. 



Shell narrowly pyramidal, a little more than three times as 

 long as wide, shining-white and smooth. Spire-whorls eight in a 

 length of six millimetres, of moderately rapid increase, flat, 

 separated by a well-defined linear suture. Last whorl with a 

 regularly convex base ; aperture pyriform, with a stout elevated 

 plait at the origin of the columella, inner front angle of aperture 

 slightly effuse and thickened with a slightly reflexed edge. 

 Length, 6-25, vix ; breadth, 2*0, vix, mm. 



If Syrnola is a valid genus, then the present species belongs 

 thereto. Among Australian species known to me by actual 

 specimens it has the following alliances. It is narrower than 

 S. jucunda and broader than *S'. tincta, but differs from both in 

 its longer aperture and the far-backward position of the columella- 

 plait ; in respect of its apertural characters, it resembles 

 JS. infrasulcata, mihi, which is, however, a robust shell and has 

 a sculptured body-whorl. 



The species-name is in compliment to Mr. J. W. Jones, Con- 

 servator of Water, whose continued interest in the promotion of 

 stratigraphical and palaiontological investigations is abundantly 

 evinced in the present communication. 



