G38 APPENDIX. 



operculigerous lobe long, cylindrical, bearing the operculum on 

 its truncated extremity. 



Operculum claw-like, with a spiral nucleus situated near tbe 

 internal or thickened border. 



Shell spiral, turbinate, imperforate; spire elevated, whorls 

 rounded ; aperture oval, produced in front. 



Ex. E. Macdonaldi, H. and A. Adams, pi. 138, fig. 2. Oper- 

 culum, E Macdonaldi, fig. 2, a. Shell, E. Macdonaldi, fig. 2, b. 



This genus was observed by Mr. Macdonald during the voyage 

 of H.M.S. "Torch "from Sydney to Moreton Bay. He de- 

 scribes the little animal as wielding its clawed operculum, ap- 

 parently as a means of defence, with great dexterity, and 

 making skips and jerks by means of its complex foot, after the 

 manner of Nassa and Strombus. 



Genus GEMELLA, H. and A. Adams. 

 (Fam. macgillivrayiid^:.) 



Operculum paucispiral, the lines of growth well marked. 



Shell sub-globose, thin, pellucid, not umbilicated ; spire small, 

 compressed, whorls few, smooth ; aperture large, entire. 



Ex. G. hyalina, II. and A. Adams, pi. 138, fig. 3, 3, a. 



For this genus we are also indebted to Mr. Macdonald, who 

 met with it very commonly in the South Pacific. He observes 

 that the foot is not unlike a broad or square-toed shoe in form, 

 receiving or bearing the remainder of the animal and the shell. 

 The little animal creeps on its foot with great rapidity, appearing 

 rather to slide along than progress by a vermicular movement, 

 and by spreading out and hollowing this organ at the surface of 

 the water, by the same instinct which prompts the fresh-water 

 Limnsead to form a ready boat of its foot, this shell-pi'otected 

 speck buoys up its tiny body, cast abroad, though not lost, in the 

 ocean's immensity. 



