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POPULAR CONCHOLOGY. 



posed of two primary teeth (one of which is bifid) in each 

 valve ; no lateral teeth ; ligament ex- 

 ternal ; no lunule ; muscular scars 

 nearly equal, ovate ; pallial impression 

 single. Animal shaped as the shell; 

 mantle open in front, simple at the 

 edges ; siphons wanting (?) ; branchial 

 lamillae on each side of the body not 

 united into one ; labial palpi developed, 

 triangular; foot lanceolate.* — 10 species; also fossil. 



Shells without any colour, found in the Mediterranean, 

 and D. (Tellina) rotundata on the British shores. 



Diplodonta. 



Ungulina transversa. 



Ungulina. Daudin. — Shell transverse or almost 

 round ; valves nearly equilateral, and 

 not gaping ; one bifid cardinal tooth 

 in each valve, and at the side a long 

 pit containing the ligament; no la- 

 teral teeth. Animal, having sessile 

 siphons, and somewhat similar to 

 Lucina. — 2 species. 



These shells are small, thin, transparent, and have a 

 very strong epidermis; they appear to be found in the 

 fresh waters of Senegal. 



Scacchia. Philippi. — Shell rather oval, equivalve, 

 inequilateral, very thin and smooth, closed; the hiDge 

 shows one or two small cardinal teeth, and slight side 

 teeth; two small, tolerably even, round muscular im- 

 pressions and no sinus. Animal, with the mantle almost 

 entirely cloven, closed behind, with a single opening ; the 

 foot is compressed, tongue-shaped, separated by means of 



* Forbes's British Moll. 



