22 



There is a certain resemblance between Z7. Johnstooii and 

 Z7. Fachyodon, Ludwig* (from tlie Tertiary strata of Oj^pen- 

 lieim, on the Ehine), when viewed from the side, but the 

 compressed form of the valves at once separates our shell 

 from this species. Several species of TJnio have been 

 desciibed from the Wahsatch group of the Wyoming Ter- 

 tiary strata, by Dr. C. A. White,t but none of them appear 

 to correspond with our TJ. Johnstoni. 



Of the two species described from New Zealand strata, 

 neither will correspond with our form. One, U. AucMandica, 

 is oblong and compressed ; the other, TJ. inflata, Hutton, is 

 oval and ventricose ; lastly, U. Johnstoni, is quite distinct 

 from my m.s. species, U. Wilkinsoni, of the Gulgoug deep 

 leads. 



Sandberger figure a number of fossil Unios in their 

 ^' Susswasser Conchylien," none of which need be compared 

 with the Tasmanian specimens. 



Loc. and horizon — In a ferruginous clay, Tertiary beds of 

 the Tamar River, between Whirlpool reach and George 

 Town, Tasmania (British Museum, Milligan Collection, Reg. 

 No. 9628) ; Muddy Creek, West Tamar {U. M. Johnston). 

 Genus Anodonta Cuviee. 



Anodonta (?) Tamarensis. 8].). nov. Fig. 3 and 4. Sp. 

 chars. — Shell transversely -obliquely-oval, generally com- 

 l^ressed, iu marginal outline obliquely hatchet-shaped ; 

 anterior and posterior ends compressed, sharj:* at the margins; 

 anterior outline (margin) rounded ; posterior outline obliquely 

 truncated in the upj^er portion, rounded in the lower ; hinge 

 line horizontal, straight ; ventral margin rounded obliquely 

 from the anterior end ; beaks near the centre of the hinge, 

 but, as regards the whole shell, more anterior, not inflated, 

 but much decorticated : diagonal ridge and posterior slope to 

 all aj^pearances not defined ; convexity of the shell not great, 

 the most convex point being below the beaks, at about the 

 middle of each valve; angle formed by the hinge line and trun- 

 cated posterior margin = 143 ^ . Shell substance much eaten ; 

 surface decorticated, but, apjjarently covered with numerous 

 concentric superimposed layers of epidermal matter, fol- 

 lowing the marginal outline of the shell. Length, 3 in. 

 7 lines ; breadth, 2 in. 3 lines ; thickness of the united valves, 

 1 in. 3 lines. 



Ohs. — This shell is manifestly so different from the pre- 

 ceding, both in marginal outline and general form, that, 



* Danker's Palreoutographica, 1863, xi. lief 3, p. 170 to 22, f. 1-5. 

 t Bull, n.s., Geol. and Geogi-aph. Survey of the Territories, 1877, iii. pp. 

 603-606. 



