New and Rare Foss/h. 303 



A typical valve of this species was found associated with fossils 

 of a Kalimnau facies in the Malice bore. The present specimen has^ 

 been carefully compared with living examples from the Victorian 

 coast, and found to be identical in the minutest particulars. 



Distribution.— BovG 2, 198-2U0 feet. 



Genus GLYCLMERIS, da Costa. 



Glycimehis maccuyi, Johnston sp. (Plate XXIV., Figs. !•")). 



Pectunculus laticosfafns, McCoy, non Quoy and Gaimard,. 

 1875. Prod. Pal. Vict. dec. ii.. p. 26. pi. xix.. figs. 

 10- U. 



P. M'Coiji. Johnston, 1885, Proc. R. Soc. Tas. for 1884, p.. 



199. 

 P. McCoi/ii, Johnston, Tate, 1886. Trans. R. Soc. S. Austr., 

 vol. viii. p. 137. 

 From a lengthy and minute examination of numerous specimens 

 of the above species from Balcombian, Janjukian and Kalimnan 

 strata, we are able to make the following observations. The 

 examples afford an interesting study of a series of mutations of one 

 species through a comparatively long geological epoch, which 

 species meantime preserves its essential characters. 



1. The fossil specimens figured by McCoy under the name of 

 Pectunculus laticostatus, Quoy and Gaimard, represent the toler- 

 ably distinct mutations (in Waagen's sense) of the one form. They 

 are : — 



Form a. — A small shell from Grice's Creek (Balcombian) : length 

 (ant. -post.), 14.75 mm.; height, 14 mm. (PI. xxiv.. fig. 1). Also 

 larger valves from Corio Bay (Janjukian), length. 42.25 mm. ; 

 height, 42 mm. Characterised by 32 riblets in the small shell and 

 by 34 riblets in the large one. 



Form h. — A large and ponderous shell from Bird Rock (Jan- 

 jukian) : length, 64 mm. ; height, 67 mm. Characterised by 40 

 riblets, practically equal to that of the recent Glijcimeris laticos- 

 tatus, Q. and G. (PL i. figs. 2, 3.) 



2. The typical form of G. maccoyi diagnosed by R. M. Johnson 

 has 29 riblets. (PI. xxiv. f. 4.) His type form was described from 

 the Table Cape beds (Janjukian); a similar form, but smaller, is- 

 found in the Balcombian of Mornington, Muddy Creek older beds^ 

 and the younger series at Corio Bay. 



