608 



examples they are quite irregular. The varices disappear in 

 the later whorls, and the axial costae also gradually fade out. 

 The spiral lirae (with two to five intervening striae), about 

 six in the spire whorls and twice as many in the body whorl, 

 retain their validity. The thickly-glazed inner lip gives the 

 impression that the callus of the posterior half has been first 

 laid down over a circular area, and the anterior half laid 

 down upon this over an area with a shorter radius, sO' that 

 the edges of the areas meet each other at a wide angle, and 

 the edge of the anterior circular area is continued into the 

 aperture as a raised curved plait or carination. Its lower edge 

 curves round anteriorly, and forms wdth the basal lip a 

 shallow wide sinus with a slightly everted edge. The proto- 

 conch consists of two smooth convex homostrophe whorls. The 

 ornament is composed of squarish light-chestnut spots imme- 

 diately below the suture, with smaller spots more or less 

 distantly articulating the lirae, and sometimes also so disposed 

 as tO' form curved axial narrow flames of dots. 



It is very closely allied to the fossil Diastoma provisi, 

 Tate, Journ. and Proc. Roy. Soc. N.S. Wales, vol. xxvii., 

 1893, p. 177, Miocene and Older Pliocene (now recognized 

 as Older and Newer Pliocene). Tate diagnoses between the 

 two. He also shifts both species from the genus Mesalia 

 to Diastoma y Deshayes. He writes, "Cossman, to whom the 

 fossil was sent under the above name" (Mesalia 2}r6visiJ, 

 "informs me that it is a Diastoma; from him I have received 

 examples of several species of Diastoma and Mesalia from the 

 Parisian Eocene. This material permits me to affirm that 

 M. provisi, Mihi, and M. melanioides, Rve. , are congeneric 

 with D. costellatum, Lamarck; whilst Mesalia xulcaia, 

 Lamarck (non sulcata, Qfvajy — hrevialis, Lamarck), is of a 

 totally different type. Diastoma simulates Mesalia, but the 

 latter has a sinuated outer lip, whilst the spiral carination 

 of the columella of Diastoma is quite a different feature from 

 the slight twist of the columella-margin of Mesalia: more- 

 over, Diastoma is more or less variced. Mesalia belongs to the 

 Turritellidae ; Diastoma, which has been located in at least 

 two families, finds a resting place in Cerithiidae, it may be 

 viewed as a Melania-like Cerithium." 



E. A. Smith, in his review of the Genus Mesalia, loc. 

 cit., supra, does not refer to Tate^s transfer of J^l . melanioides, 

 Rve., to the Genus Diastoma, which, however, merits notice 

 and acceptation or refutation. 



Evening Meeting, September 14, 1922. 



