50 



A.CMMX COST AT A. Sowerhy Zool. Voy. Beag., as Patella, 

 Probably also P. alticostata, Angus. Proc. Zool. kioc. 1865, p. 56, 

 pi. 2 fig. 11. This shell has always been set down as a 

 Patella, but the animal shows it to belong to the above genus. 

 The shell is oval or elliptic, depressed and somewhat tumid, 

 apex submedian with from 12 to 30 coarse-rounded rough 

 uneven ribs, irregularly marked with lines of growth which 

 makes them almost nodular. Interstices concave, transversely 

 barred at intervals with black or brown lines, which are the 

 remains of successive marginal marks ; they are seldom 

 regular, appearing at intervals and frequently corroded away ; 

 interior porcellanous, white or faintly bluish white, ir- 

 regularly stained pale brown, shining ; margin undulating, 

 with a well-defined narrow brown edge, which is spotted deeper 

 brown or black at the intervals between the ribs ; S2:)atula 

 generally well defined, reddish brown, paler in the centre. 

 Size varying, but generally 30 to 40 mill., and the propor- 

 tions of length, breadth, and height being as 10, 8, and 4. 



Animal a dull yellow below, blending into brown at the 

 base of the foot, tentacles fine and short, with eyes at the 

 external base ; gill plume long, flat and lanceolate, flexuously 

 extended over the head ; muzzle yellow, and notched below ; 

 inner hp cartilaginous and transparent, with a shelly appendage 

 coming down from above horizontally acrossthe tongue and ap- 

 parently holding the food against the rasp ; jaws cartilaginous, 

 crescentic, but pointed and attached; very massive red muscles; 

 odontophore one and a half the length of shell, with broad 

 membranaceous expansion at mouth ; teeth in pairs, alternat- 

 ing large and small, the small ones close together and some- 

 what narrow ; the larger with a broadly semi-circular edge 

 and a small lateral cusp on the outer side. 



This Acmsea is equally common in South Australia and 

 Tasmania. It exists between the tidal marks, and is of such 

 a large size that it was never suspected to be other than a 

 Patella. Tet in Australia the Acmsea genus has species quite 

 as large as Patella, though this I think is a new fact in 

 zoology. They feed on ulva, and are considered better eating 

 than true limpets, though these shellfish are seldom eaten in 

 Australia. 



AcM^A SEPTiFOEMis. Quoy and Gaimard, Voy. de V Astro- 

 labe, pi. 71, f. 43, 44. A. scahvilirata, Angas, Zool. Proc. 

 1865, p. 154, Tectura septiformis, Cox Exchange list: Sydney, 

 1867. Patella cantharus, Reeve (probably) pi. 4, f. 131. 



This shell varies so much in colouring and the fine mark- 

 ings that I am afraid it has received a longer list of syno- 

 nyms than I can enumerate. The shape of the shell is, how- 

 ever, constant. It is small, broadly ovate, depressed, apex 

 acute, submarginal ; in young well preserved specimens, 



