396 G. n. Prltchard: 



latter portion of its course is not absolutely distinct in the 

 specimens Before me. 



Dimensions. — Longitudinal diameter, 195 millimetres ; trans- 

 verse diameter, 185 mm. ; height, 55 mm. ; Periproct, *20 mm. 

 by 15 mm. ; Peristome, 23 mm. by 4 mm. ; thickness of test, 

 2 mm. 



Liocality. — Pol3'zoal Limestones of the Filter Quarries, Bates- 

 foid, Moorabool Valley. — Balcombian-- Eocene. 



Observations. — In this species one is struck by the very large 

 size associated with a comparatively thin and weak test, and 

 this no doubt accotints for the large number of fragments or 

 crushed specimens obtainable as against perfect examples, which 

 have hitherto been very rare. This form aj^pears to be one of 

 the largest, if not the largest, species of the genus ; but I am 

 not in a position to assert positively on this point, as I have not 

 yet had access to all the described species. 



From Pericosinus gigas, McCoy, which, by the way, is also 

 referable to the genus Linthia, the present species differs in its 

 much more depressed form, its profile views being very dis- 

 tinctive, the anterior notch shows many divergent features, the 

 ornamentation is of a much finer character, the tubercles are not 

 so ornate, the fascicles are narrower and follow .-i rather different 

 course, and the anterior petals diverge at a much smaller angle, 

 and the poriferous plates are more croAvded. The proportion 

 of height to length in P. gigas is given as 45 : lO'J, whilst in 

 the present species it is only 28.2 : 100. 



Tl. —Linthia gigas, INlcCuy, sp. 



1882. Pericosinus gigas, McCoy. Prod. Pal. Vic, Dec. 



vii., pp. 15, 16, plates 64, 65. 

 1892. Pericosmus gigas. Hall and Pritchard. Proc. Roy. 



Soc. Vic. vol. iv., n.s., pt. 1, p. 18. 



1892. Pericosmus gigas, Pritchard. Ann. Report South 



Aust. School of Mines and Industries, p. 185. 



Observations. — The original records of the occurrence of this 



species have unfortunately been of a somewhat ambiguous 



nature. The type was indicated by McCoy as from the banks 



