CONCHIFEEA. 413 



straigM, gaping, posterior rounded, Tisually close ; nmbones 

 apart, eared ; valves smooth, punctate -striate, or radiately 

 ribbed and imbricated; hinge area triangular, cartilage pit 

 central ; adductor impression lateral, large, double ; pedal 

 scars 2, small. 



Animal, mantle-margins separate, inner pendent, fringed 

 with long tentacular filaments, ocelli inconspicuous ; foot 

 finger-like, grooved ; lips with tentacular filaments, palpi 

 small, striated inside ; gills equal on each side, distinct. 



The shell is always white ; its outer layer consists of coarsely- 

 plicated membranous lamellae ; the inner layer is perforated by 

 minute tubuli, forming a complete network. (Carpenter.) 



The Limas are either free or spin a byssus ; some make an 

 artificial burrow when adult, by spinning together sand or coral- 

 fragments and shells, but the habit is not constant. (Eorbes.) 

 The burrows of Z. hians are several times longer than the shell, 

 a,nd closed at each end. (Charlesworth.) "This species is 

 pale or deep crimson, with an orange mantle ; when taken out 

 of its nest it is one of the most beautiful marine animals to look 

 upon, it swims with great vigour, like the scallop, by opening 

 and closing its valves, so that it is impelled onwards or upwards 

 in a succession of jumps. The filaments of the fringe are 

 easily broken ofi", and seem to live many hours after they are 

 detached, twisting themselves like worms." (Landsborough.) 

 L. spinosa has conspicuous ocelli, and short filaments. 



Sub-genera, Limatula, S. Wood. L. sub-auriculata, PL XYI., 

 Fig. 13. Valves equilateral; 8 species. Greenland — Britain. 

 Fossil, Miocene — . Europe. 



Limcea, Bronn. L. strigilata, PI. XYI. Pig. 14.* Hinge 

 minutely toothed. 



Fossil, 4 species. Lias — Pliocene. The recent Limcea? 

 Sarsii (Loven), Norway (=L. crassa of the ^gean ?) has the 

 mantle-border plain. Some of the larger recent species have 

 obscure lateral teeth. 



Distribution, 20 species. Norway, Britain, West Indies, 

 Canaries, India, Australia ; 1 — ] 50 fathoms. The largest living 

 species {L. excavata, Chemn.) is found on the coast of Norway. 



i'^osstZ, 200 species. Carb.? Trias — . United States, Europe, 

 India. The so-called Plagiostoma spinosum is a Spondylus. 



Spondylus (Pliny) L. Thorny- oyster. 



Type, S. g8edaroj)us, L. 



Example, S. princeps, PL XVI., Eig. 15 



* Aitev Bronn ; the figure in Brocclii does not show the teeth. 



