CONCHOLOGY. 91 



T. glohosa. The globose Terebratula. 

 Species smooth, with the valves rounded at their anterior 

 edge. 



T. caput serpenfis. The Serpent's-head Terebratula. 



Species grooved, with the summit or heel of the large 

 valve deeply hollowed even to the edge of the articulation ; 

 the slope rounded ; the valves sub-bilobate by the apparent 

 slope of the anterior edge. 



3. Lingula. One species. 



The valves of this genus are united by means of a tubular, 

 fleshy, or membranous peduncle surrounding the narrow part 

 of them, and of which the base is affixed to marine sub- 

 stances. 



Shell covered with epidermis, sub-equivalve, equilateral, 

 depressed, elongated, truncated anteriorly, summit middle 

 and posterior, without trace of ligament, but supported at 

 the extremity of a long fibro-gelaiinous peduncle, which at- 

 taches it vertically to sub-marine bodies ; multiple muscular 

 impression. 



L. anatina. The Duck's-bill Lingula. PI. 17, fig. 2. 

 Covered with a green, shining epidermis, shaped hke a 

 duck's bill, and having a cylindrical peduncle. 



