New and Rare Fossils. 305 



A solitai-v t'xainj)k' of the alxivc species was found in the Malloe 

 material. It is (juitf typical l)(>tli in the eostate ornament witli blunt 

 jiroeesses an<l in the heavy chaiaiter of the shell. It is most inter- 

 esting to Jiieet with this s|n'(ies. which has not l)eeTi recorded south 

 of Port Jaeksdii as a living shell. U>y it occurs here in presumably 

 passage beds between the Janjukian and Kaliiiinan series of the 

 Mallee. 



A well-known KaliTiman offshoot of this polyphyletie form of 

 Triijoiiiii is si'cn in 7'. hoiritil .McCoy, which has the same ornament 

 (see pi. XXV. tig. 10). but is stouter, heavier and with fewer libs; a 

 form moi'e adapted to shore conditions, as denoted by the fauna 

 iiocompanying tliat shell. 



Distrihufioii. — Bore 9. M'^-'.VIT) feet. 



TuinoNiA mak«;akitacI';a, Lamarck, var. acuticostata, McCoy. 

 (PI. XXVI., Figs. Vl and Via, b). 

 Triijoiila aciificosfafa, McCoy. 1866. Geol. Mag. vol. iii. pp. 

 481, 482, fig. 1. Idem. 1875. Prod. Pal. Vict. dec. II.. 

 p. 21, pi. xix., figs. 1, 2. T. niar;/ar/f(iren. Lam. var. 

 acuticostata, McCoy, Hedley, 1902, Mem. Austr. Mus., 

 Mem. IV. pt. 5. p. :i01, tigs. 47. 48. 



McCoy, in his original description of the al)ove fossil, alludes to 

 the distinction between this variant of 7'. iiuirgaritacea, Lam. and 

 the species, T. lamarcki. Gray, and T. pert i unto. Lam. ( = T. mar- 

 gar itacea) in having a " remarkable compression of the ribs into 

 acute angular ridges; and from the same cause the spinous 

 tubercles do not form the broad. l)lunt. transver.se tubercles which 

 they do in the recent species, in which latter tlie ridges foini 

 broad, obtusely flattened, almost square ribs when viewed from tlie 

 margin in a position \\\ which those of the present species form a 

 series of acute angles. ""i 



That this distinction is only varietal has already been pointed 

 nut by .Ml-. Hedley (loc. supra cit. p. 301), who is not followed in 

 this, however. l)y Messrs. Pritrhard an.l (;aTlift.2 The fossil 

 examples cori-esi»ond with tiie living T. nmnjariiacfa (.see pi. xxv. 

 tig. 11), in having a lighter and less inflated shell as compared with 

 T. laiiuirchi : also in being more oblique and liaving more actite 

 ribs. It is never found lower than the Kalimnan series (Lower 

 Pliocene) in the geological scale. 



1. Loc. cit., 1875, p. -li. 



2. Pioc. Roy. Sw. Victoria, vol. xvi. (n.s.), pt. i., 1904, pp. 235-237. See also Piitdiard, Vict. 

 Nat, vol. xxiil., w. (i, lOOC. p. US. 



