38 PLEUEOTOMi. 



left without any material conchological differences between the 

 two genera mentioned, and the assignment of any but typical 

 si^ecies to either of them must remain doubtful. It is highly 

 probable, however, that a special study of the protoconchs, and 

 the mode of growth of the shells as found in the fossil condition, 

 will assist in clearing up many difficulties. 



Very few of the Australian Tertiary species of PLEUEOTOiiin^ 

 have been described ; of these some have never been figured, and 

 the descriptions of the remainder are often so imperfect as to 

 render identification impossible. Several forms new to science 

 are now recorded. 



Genus PLEUROTOMA, Lamarck. 

 [Mem. Soc. Hist. Nat. Paris, 1799, p. 73.] 



Shell turriculated, spire long ; collumellar margin smooth ; outer 

 margin of the aperture with a narrow, deep sinus, situated some 

 distance from the suture ; canal long and straight. 



Type. — Murex habylonius, Linnseus. 



Pleurotoma murndaliana, Tenison-Woods. 



1879. Fleurotoma murndaliana, Tenison-'Woods, Proc. Linn. Soc. N.S.W. 



vol. iii. p. 226, pi. xx. fig. 5. 

 1889. Pleurotoma murndaliana, Deimant, Trans. Eoy. Soc. South Aust. 



vol. xi. p. 44. 

 1893. Pleurotoma murndaliana, Tate and Dennant, id. vol. x\ii. pt. 1, p. 221. 



Protoconch composed of three elongate turns, the initial portion 

 being slightly inflated, whilst the anterior turns are obtusely 

 carinate. Shell narrow, elongate ; whorls ten in number, slightly 

 convex, and having several bold, irregular, spiral threads or 

 ridges, rather rugose where crossed by growth-lines, and some- 

 what granulated in the neighbourhood of the sinus. Canal long, 

 slender, and twisted ; outer margin serrate, sinus large and deep, 

 and situated some distance from the suture. 



Dimensions. — Length 47 mm.; breadth 13 5 mm.; length of 

 aperture 20 mm. 



Form, and Loc. — Eocene : Yictoria. 



73232. A variation in which the whorls of the spire carry three 

 acute spiral ridges, or keels, the posterior of which has developed 

 a median sulcus, and is granulose. From Brighton. Purchasid. 



