THE VICTORIAN NATURALIST. 119 



variety of Trigonia margaritacea, Lamarck.'^ Fortunately the 

 specimens cited by M'Coy as the living representatives are to be 

 seen in the National Museum, Melbourne, and a critical examina- 

 tion of them shows a form of comparative rarity, and a variety of 

 T. margaritacea, but, nevertheless, easily distinguished from the 

 fossil T. acuticostata. As the forms originally described by 

 M'Coy were the fossils, there can be no reasonable objection to 

 retaining the above name for them, especially as the lapse in the 

 identification of the recent species can now be so satisfactorily 

 explained. 



The principal horizon for the fossils is from the Miocene or 

 Kalimnan of Victoria and South Australia, and they are fairly 

 common from the sandy clays of the Beaumaris beds, originally 

 referred to by M'Coy as " Older Pliocene beds of Mordialloc." 

 In dealing with " The Growth Stages in Modern Trigonias," Mr. 

 T. S. Hall states that there is a similiarity in the prodissoconch 

 of T. margaritacea and T. acuticostata, but a difference in the 

 brephic stage ; also that T. acuticostata is said to be most closely 

 allied to T. lamarckii. The latter remark does not appear to be 

 altogether in conformity with general opinion, for, even when 

 M'Coy described T. acuticostata, he says : — " The present species 

 is easily distinguished, even in fragments, from the T. lamarcki, 

 T. pectinata, and other recent species by the character indicated 

 in the specific name, &c." 



NiSO KIMBERI, sp. nOV. 



Description. — A narrow, elongate shell, with a very acute 

 apical angle of about i8 degrees, the embryonic portion consist- 

 ing of about one whorl and a half, smooth and shining, and 

 somewhat blunt at the extreme tip. Spire-whorls, eleven, strongly 

 flattened between the sutures, and perfectly smooth and shining, 

 the overlapping of the whorls leaving only a slightly impressed 

 suture ; there are faint sigmoidal lines of growth, with occasional 

 and periodic strong development of variceal-like breaks. Body- 

 whorl rounded off suddenly to the base, which is convex to the 

 deep but narrow and margined umbilicus. Aperture narrow 

 ovate, and posteriorly running out acutely to the angulation of 

 the body-whorl, anteriorly narrowed to the columellar junction 

 and slightly effuse ; outer lip thin at the edge and sigmoidally 

 arched. 



Dimensions. — Length, ii mm.; breadth of body-whorl, 4 mm. ; 

 length of aperture, 2.5 mm. ; breadth of aperture, i mm. ; 

 diameter of umbilicus, about i mm. 



Loc. — Lower beds of the Aldinga series, South Australia, 

 collected by Mr. W. J. Kimber. Jan-Jukian — Eocene. 



Obs. — This new species of Niso makes the second of this 

 genus represented in our Older Tertiaries, and is named after Mr. 



* Trigonia margaritacea, var. acuticostata, Hedley. Mem. Aust. Mas., 

 vol. iv., pt. 5, pp. 301, 302, 1902. 



