434 MOLLUSCA FROM THE HOPE ISLANDS, N. QUEENSLAND, 



Arcopagia dapsills, n.sp. 

 (Plate xxxviii., fig.33.) 



Shell small but comparatively solid, oblong-equilateral, the 

 dorsal margins rather straight, meeting at an obtuse angle, where 

 the umbo projects suddenly and rather obliquely; anterior, ventral, 

 and posterior margins rounded. Colour white. The whole surface 

 is minutely reticulated by the intersection of about one hundred 

 fine radial threads, with concentric threads of equal size and 

 space. In addition, there are wide elevated concentric folds, 

 varying from none to a dozen, and which ma}' be evenly distri- 

 buted over the disk or confined to the first third or so. These 

 coarse folds are traversed without interruption by the finer 

 sculpture. I was unable to detect the pallial scar. Length 2 '9; 

 height 2-3; depth of single valve 055 mm. 



This is the smallest Australian Arcojmgia; its shape distin- 

 guishes it from such small forms as A. elegantissima Smith, A. 

 tenuilamellata Smith, or A. fahrefacta Pilsbry. It seems to be 

 widely distributed in Queensland, for not only did we take it 

 plentifully, in 5-8 fathoms, off the Hope Islands, but I dredged 

 it previously, in 15 fathoms, ofi" the Palm Islands, and, in 17-20 

 fathoms, off Mast Head Island. Mr. H. L. Kesteven also found 

 it on the beach at Caloundra. 



Semele isoceles, n.sp. 

 (Plate xxxviii., figs. 34-36.) 



Shell small, thin, translucent, triangular equilateral, inequi- 

 valve, rather inflated. Ventral margin rounded, posterior and 

 anterior margins straight, except that the right anterior margin 

 is more curved. Colour white. Sculpture!: about twenty delicate 

 erect concentric lamellae, irregularly spaced, undeveloped towards 

 the umbo, crowded towards the ventral margin. Length 3-25; 

 height 2-9; depth of single valve 11 mm. 



This species appeared in abundance. Mr. A. U. Henn also 

 found it in blue mud, adhering to a ship's anchor, in lOJ fathoms, 

 off Bow Reef, near Cape Sidmoutli, Queensland. Its nearest 



