CONCHIFERA. 



271 



front, its margin extending considerably beyond the shell, 

 and bearing superiority a fringe of filaments, one of which 

 is much larger than the rest ; a short siphonal tube, with 

 a single aperture at the larger end of the shell ; foot thick 

 and tapering, keeled and disked, furnished with a byssal 

 groove ; branchial leaflets two on each side, and separate.* 

 — Few species. 



Two British species, one of which, L. squamosus, Mr. 

 Alder says, has a long filament which waves to and fro 

 when the animal creeps, as if it were for the purpose of 

 feeling the way ; it spins a few threads. 



Cyamium. Philippi. — Shell equivalve, transverse, some- 

 what inequilateral, thin, scarcely gaping ; two cardinal teeth 

 in each valve, no lateral teeth ; the ligament is double, 

 the inner, is situated in a triangular pit which is formed 

 in both valves behind the cardinal teeth; the pallial 

 impression simple, without a sinus. — 1 or 2 species. 



Philippi mentions, C. antarcticum, a native of Patagonia; 

 Loven alludes to another. 



Montacuta. Turton. — Shell small, thin, equivalve, 

 inequilateral, transversely oblong, or obliquely 

 oval, surface smooth or concentrically striated, 

 or rarely radiatingly furrowed ; beaks inflect- 

 ed; inner margins smooth; hinge margin 

 with a triagonal incision and cartilage pit, and Montacuta. 

 a pair of diverging laminar teeth in one or 

 both valves; ligament internal; muscular scars subor- 

 bicular; pallial impression simple. Animal oblong, its 

 mantle freely open in front, with simple margins; not 

 furnished with siphonal tubes posteriorly, a single siphonal 



* Forbes's British Moll. 



