PERMO-CARBONIFEROTJS PELECYPODA— ETHERIDGE. 179 



in question to either Cardinia, Orthonota, or Pleurophorus appears 

 to be impossible. It is a remarkable fact that the authors who 

 have dealt with these shells invariably describe the cardinal 

 margins as linear, narrow and concave. Indeed the remarks 

 of both Dana and Morris indicate their mental uncertainty as to 

 what genus they should be referred to. 



I therefore propose, under the circumstances, the genus Stutch- 

 buria for the reception of Orthonota 1 costata, Morris, and if 

 differing from it 0. ? compressa also, in honour of Samuel Stutch- 

 bury, the pioneer Naturalist, and one of the two pioneer Geologists 

 of Australia. 



The characters of the new genus will be as follows : — 



Shell transversely elongate, equivalve, very inequilateral, the 

 posterior end the longer, more or less compressed, closed, test 

 thin; posterior slopes always rounded; a mesial sulcus sometimes 

 present in each valve ; edentulous ; ligament supported on the 

 thickened hinge plates ; dorsal or cardinal margins erect and 

 sharp ; urabones very anterior ; the anterior adductors large, 

 with single smaller supplementary scars (?) between them and the 

 umbones, in the cavity of which there are at times other scars ; 

 posterior adductor scars large, but less defined ; pallial lines 

 simple ; sculpture concentric and at times radiate. 



The form, edentulous nature of the thin shell, internal ligament, 

 and often radiate sculpture indicate the Solemyidfe as the family 

 to which Stutchhuria should be referred. The representatives of 

 this family are Solemya, Janeia, and Clinopistha, to which Mr. 

 W. H. Dall has suggested* the addition of Orthodesnia and 

 Whitevesia. Now, the proposed new genus, although resembling 

 Solemya in its edentulous nature, and simple pallial line, differs 

 entirely in having the ligament practically posterior, and no trace 

 of the umbonal ligamental clefts. From Janeia it is easily distin- 

 guished by the equality of its valves, and from Clinopistha by out- 

 line, the presence of an internal ligament, and by the fact that the 

 umbones are anterior and not posterior. The reference of Ortho- 

 destna, as described by Hall and Whitfield, to the Soleniyidse does 

 not appear to be well established, but two of the species so 

 described by Ulrich, from the Lower Silurian of Minnesota 

 approach much nearer to Stutchburia, especially in their muscular 

 scars. 



With regard to Whitevesia, the edentulous nature of the hinge, 

 simple pallial line, and internal ligament, indicate a departure 

 towards our shell, but the grooved hinge plate, and both external 

 and internal ligament if present, but of which there seems to be 

 some doubt, as well as the very much feebler muscular scars, 



* Dall— Trans. Wagner Free Inst., ill., 1895, p. 515. 



