468 MAKUAL OF THE MOLLTTSCA. 



Animal (of C. soknoides) with mantle -lobes united, cirratel 

 behind ; pedal opening moderate ; foot small, compressed, -with 

 a large byssal pore near the heel ; siphons short, conical, unequal, 

 cirrated externally ; orifices fringed ; palpi small ; gills unequal, 

 the outer narrower and shorter, deeply lamellated, united 

 posteriorly, the inner prolonged between the palpi. 



Animal of Cpjmcardia rostrata, Lamarck, Philippines (Fig. 

 300), with mantle-lobes united, 

 and covered with wrinkled epi- 

 dermis ; siphonal orifices fringed ; 

 gills deeply plicated, anterior 

 part of the outer gill united to 

 the inner ; dorsal border narrow, 

 plaited ; adductor muscles of two 



Fig. 261. Cypricardm. elements. 



Distribution, 13 species. Eed Sea, India, and Australia. In 

 crevices of rock and coral. 



Fossil, 60 species. Lower Silurian — . North America and 

 Europe. 



? Suh-genera. Coralliophaga, Bl. C. coralliophaga, Lamarck. 

 Shell long, cylindrical, thin, slightly gaping behind ; hinge- 

 teeth 2.2, and a laminar posterior tooth ; pallial line with a -^ide 

 and shallow sinus. Distribution, 5 species. Mediterranean, in 

 the burrows of the Lithodomus ; sometimes two or three dead 

 shells are found one within the other, besides the original owner 

 of the cell ; South Sea. 



? Cypricardites, Conrad (part). An. Geol. Eep., 1841. (San- 

 guinolites, M'Coy.) Employed for Cypricardia-shaped shells of 

 the palseozoic rocks ; some of them are more nearly related to 

 Modiola (v. Modiolopsis, p. 422), but they bear no resemblanpe 

 to Sanguinolaria. 



Ooniophora, Phillips, 1848. Cypricardia cymbseformis, Sby. 

 Upper Silurian, Britain [Mytilidce ?). 



PLEUROPnoRUS, King, 1848. 



Tijpe, P. costatus, Brown. Permian, England. (Pal. Trans., 

 1850. PI. XV., Figs. 13—20.) 



Synonyms ? Cleidophorus, Hall (cast only). Unionites, Wissm. 

 ? Ma3onia, Dana. 



Shell oblong ; dorsal area defined by a line, or keel ; umbones 

 anterior, depressed; hinge-teeth 2.2; laterals 1.1; elongated 

 posterior ; anterior adductor impression deep, with a small pedal 

 scar close to it, and bounded posteriorly by a strong rib from the 

 hinge ; pallial line simple. 



