MACTRA.— Plate XV. 



Hab. New Zealand ; Major Greenwood. 



A solid opake-white shell, covered towards the margin 

 Avith a clear thin straw-coloured epidermis, having the an- 

 terior lunule very large and peculiarly wrinkle-edged. 



Species 77. (Mus. Brit.) 



Mactra Byronensis. Mact. testa ovata, solidimculd, 

 gibbosa, opaco-albd, aquilaterali, antice rotimdatd, 

 postice obtuse siibangvlatd ; lumdd indistinctd; i/m- 

 bonibus parvis, subreinotis. 



The Byron Mactra. Shell ovate, rather solid, gibbous, 

 opake-white, equilateral, anteriorly rounded, poste- 

 riorly obtusely slightly angled ; lunule indistinct ; 

 umboes small, rather distant. 



Mulinia Byronensis, Gray in Brit. Mus. 



Hah. South America ; Capt. Lord Byron. 



An opake-white solid shell, of somewhat gibbous oval 

 form, with little or no sculpture or inequality of growth. 



Species 78. (Mus. Brit.) 



Mactua exalbida. Mact. testa subquadrato-ovatd, ver- 

 sus marginem compressd, calcareo-albd, irregulariter 

 rngoso-striatd, epidermide tenui stramined sparsim in- 

 dutd, incstjuilaterali, latere antico brevi, rotundato, 

 postieo oblique rotundato, tmdto longiore ; lunula vix 

 nulla ; umbonibus subremotis. 



The very white Mactea. Shell somewhat squarely 

 ovate, compressed towards the margin, chalk-white, 

 in'egularly roughly striated, sparingly covered with a 

 thin straw-coloured epidermis, inequilateral, anterior 

 side short, rounded, posterior obliquely rounded, 

 much longer ; scarcely any luuule ; umboes rather 

 distinct. 



Mulinia e,xalbida. Gray in Brit. Mus. 



Hab. South America ; Capt. P. P. King. 



Of an eroded chalk-white character, roundly oblong- 

 produced on the posterior side. 



