52 SYNOPSIS OF THE CHARACTERS OP^ THE 



Edmondia (?) COMPRESSA. M'Coy. (PL XIII. fig. 10). 



Sp, CA.— Transversely oval, evenly convex, no posterior ridge or diagonal gibbosity ; beaks small, close to 

 the anterior end ; anterior end sbort, rounded ; ventral margin convex, posterior end obtusely rounded ; surface 

 marked with fine, irregular, concentric wrinkles of growth. 



I have placed this handsome fossil provisionally in the genus Edmondia of Kouinck, it resembles the Lu- 

 traria prhnceva, Portk., but is smoother, and wants the large, prominent beaks, diagonal gibbosity, and twisted 

 appearance of the posterior side, found both in that species, and in the U. Urii, to which it is allied. Length 

 one inch, three lines, width two inches one line. 



LUTRAEIA ELONGATA. M'Col/. (PL VIII. fig. 3). 



Sp. Ch. — Twice as wide as long, convex; beaks large, prominent, slightly flattened; anterior end short, 

 rounded ; posterior side very much elongated transversely, recurved, truncated at the extremity ; dorsal and ven- 

 tral margins nearly parallel ; surface marked transversely with wrinkles parallel with the front margin, and 

 truncated posterior end. 



This curious little species is very rare, only one specimen having as yet occurred. Length four lines and 

 a half, width ten lines. 



LuTRAEiA PRiscA. M'Coy. (PL XII. fig. 4). 



Sp. Ch. — Shell transversely elongate, oval, convex, smooth, or slightly striated concentrically; posterior 

 end narrowed, rounded, subtruncate, ventral margin very convex ; beaks prominent, large. 



This shell is much less transverse than the L. primava, Portk., that species being much wider in propor- 

 tion to the length, it also ha^he ventral margin nearly straight, while it is nearly semicircular in the present 

 species. Length two inches five Unes, width three inches nine lines. 



Mactra incrassata. M'Coi/. (PL XIX. fig. 8). 



gp^ 0i_ — Obtusely trigonal, width about one-sixth greater than the length; convex; beaks central, large; 

 anterior and posterior ends equal, obtusely rounded ; surface marked with several strong, distant, irregular, 

 thickened marks of growth ; between which, especially towards the margin, are finer, transverse lines of growth. 



This fine species resembles the recent M. solida in most of its characters, but is considerably larger. Length 

 two inches seven lines, width two inches eleven fines. 



Mactra ovata. il/'Coj/. (PL XI. fig. 3). 



Sp. Ch. Transversely ovate, convex, smooth; beaks small, subcentral, nearest the anterior side; anterior 



side rounded ; posterior side obtusely pointed ; posterior area compressed. 



When examined with a lens, there appear some faint, transverse striae. Length seven lines, width nine 

 lines. 



Kellia gregaria. M'Coy. (PL XI. fig. 5). 



Sp. Ch. — Transversely oval, length three-fourths the width, compressed; beaks close to the anterior end; 

 very slightly convex ; anterior and posterior ends equal, very obtusely rounded ; surface smooth, with a lew de- 

 licate wrinkles of growth near the margin. 



In this interesting little shell the transverse wrinkles are inconstant and irregular, having precisely the 

 membranous character of those of Cyclas or Pisidium ; it seems, however, most allied to Kellia suborbicularis. 

 Length two lines, width nearly three lines. 



