48 BATHYTOMA. 



Pleurotoma, sp. indet. 



Impression, in compact "white limestone, of a large species, 

 probably one of the Pleueotomid^. It is furnished with large 

 equidistant tubercles at the periphery of the whorls, and has 

 a marginate suture, but the specimen is not well enough preserved 

 to warrant specific description. Prom the Tertiaiy of Nullarbor 

 Plains, South Australia. H. Y. L. Brown Coll. 



Genus BATHYTOMA, Harris and Burrows. 



[Eoc. and Oligo. Paris Basin, 1891, p. 113.] 



Bolichotoyna, Bellardi, Bull. Malac. Ital. t. i. 1875, p. 21 {non 

 Hope, 1839). 



Tryon,* in reviewing the genera of Pleueotomid^, follows 

 Pischer'' in including Dolichotoma as a subgenus of Genotia, and 

 remarks that in common with Pseudotoma, Oligotoma {=Astheno- 

 tomd), Roumiltia, and Cryptoconus its characters are not important. 

 The American author alluded to does not monograph the fossil 

 species, nor does he explain the matter further, so that it is 

 impossible to arrive at his precise meaning. Professor Tate^ 

 remarks that he was not satisfied that Dolichotoma is clearly 

 definable from Genotia, and therefore describes the Australian 

 species which follow as Genotia. 



I^ow the type of Genotia is Murex mitriformis, Wood, which 

 is an elongate shell with oblique suture, narrow aperture, straight 

 columella, and wide and shallow sinus situated some distance 

 in front of the suture. The type of Bathrjtoma {olim Bolichotoma) 

 is more solid and turbinate, it has a wider and relatively shorter 

 aperture, a very deep sinus situated near the shoulder of the whorl, 

 its outer margin is highly arcuate, and its columella is distinctly 

 twisted. These are differences enabling the two genera to be 

 distinguished at sight. 



M. Cossmann,* whilst drawing attention to the fact that the 

 Australian Tertiary species are, perhaps, examples of Bathytoma, 



' Manual of Conch, vol. vi. 1884, p. 154. 



- Manuel de Conchyl. 1883, p. 589. 



=* Journ. Koy. Soc. N.S.W. vol. xxvii. 1894, p. 174. 



'' Ann. Geol. Universe!, t. x. 1895, p. 756. 



