308 ME, E. A. SMITH ON THE 



variation, as the following measurements of two specimens sliow. 

 One is 127 millim. long and 65 wide, the other 124 millim. in length 

 and 69 in width. Specimens from the river Isaacs are remark- 

 able for having the hinder half considerably tuberculose. The 

 nacre is sometimes entirely white, bluish, or purplish ; but in 

 nearly every instance is more or less stained at the upper part 

 and posteriorly with livid purple, olive, or a combination of these 

 colours, difficult to define. 



The name Slmttleivorthi, which Lea in 1856 imposed upon this 

 species, was in the year previous employed by Kiister for another 

 species of this genus, also coming from Australia. The figure and 

 name only of the latter appeared in 1855 in Part 147 of the 

 ' Conchylien-Cabinet,' and the description in the following year. 

 In his " Synopsis of the Eamily Unionidae," Lea makes no 

 mention of Kiister's species. TJ. Angasi, Lea, which name can be 

 conveniently employed for this species, was described by Eeeve 

 from what I take to be the rather young state of this form. 



139. Unio depeessus, Laviarch. 



Unio depressus, Lamarck, An. s. Vert. ed. 2, vol. vi. p. 544; Delessert, 

 Recueil des Coq. pi. xii. fig. 5 ; Hanley, Recent Shells, p. 200 ; Conrad, 

 Journ. Acad. Nat. Sci. Philad. ser. 2, 1854, vol. ii. part 4, p. 295. 



NowUnio depressus. Reeve's Con. Icon. fig. 81. 



Unio rautabilis, Lea, Proc. Acad. Nat. Sci. Philad. 1859, p. 152; Reeve, 

 Con. Icon. fig. 112. 



Unio cultelliformis, Conrad, Proc. Acad. Nat. Sci. Philad. 1850, p. 10; 

 Journ. Acad. N. S. Phil. 1854, p. 295, pi. xxvi. fig. 2. 



Sai. Began Eiver {Conrad and Brit. Mus.); Eiver Nepean 

 {MacGillivray) ', Brisbane Water and Murray Eiver. 



Conrad is right, I think, in uniting his 17. cultelliformis with 

 Lamarck's U. depressus. The figure in Delessert cannot, how- 

 ever, represent the actual type, which is described as 52 millim. 

 long, for that delineated is only 40. Conrad's specimen is said to 

 be 60 millim. in length, and the largest in the Museum is 77. 



All the examples which I have seen have a slight sinuation near 

 the middle of the ventral margin, and a depression radiating from 

 the umbo to that part of the outline. The anterior muscular 

 scar is comparatively deep for so thin a shell, and of an irregular 

 form. A second small, lut very deep pit is situated just beneath 

 the anterior or cardinal teeth. This is shown in Delessert's 

 figure, and also pointed out by Conrad (Journ. Acad. JS"at. Sci. 



