SOLEMYID^. 223 



(Solemyacea.) 



Family SOLEMYID^. 



Shell elongated, transverse, equi valve, regular, very inequi- 

 lateral, gaping, thin, covered (in Solemya, the recent genus) with 

 a thick epidermis, extending beyond the shell-margins as a fringe ; 

 hinge toothless ; ligament inserted in an oblique process and 

 hidden ; pallial line simple. Along with Solemya have been 

 associated a number of fossil forms agreeing generally in the 

 shape of the shell, yet by no means of certain relationship with it. 



Solemya, Lamarck, 1818. 



Syn. — Solenom_ya, Menke, 1828, Janeira, King. 



Distr. — 6 sp. United States, Canaries, West Africa (Gaboon 

 River), Mediterranean, Australia, New Zealand ; burrowing in 

 mud; 2 fathoms. Fossil, 4 sp. Carb. — ; Britain, Belgium. 

 2 Cret. sp. ; N. America. S. Australis, Lam. (cxxiii, 63). 



Shell elongated, cylindrical, gaping at each end ; epidermis 

 dark, horny, extending beyond the margins; umbones posterior; 

 hinge edentulous ; ligament concealed ; pallial line obscure. 

 Outer layer of long prismatic cells, nearly parallel with the 

 surface, and mingled with dark cells, as in Pinna ; inner layer 

 also cellular. 



Animal with the mantle-lobes united behind, with a single 

 siphonal orifice, houi'-glass shape, and cirrated ; foot proboscid- 

 iform, truncated and fringed at the end ; gills forming a single 

 plume on each side, with the laminae free to the base ; palpi long 

 and narrow, nearly free. 



Clinopistha, Meek and Worthen, 18Y0. 



Diatr. — G. antiqua, Meek (cxx, 16, 11). Devon.; Ohio. G. 

 7'adiata, Hall. Carb. ; Ills. 



Shell transversely oval, very thin, rather ventricose, equivalve, 

 very inequilateral ; beaks near the posterior extremity and 

 directed backward, that of the- right valve with its immediate 

 apex curving under the beak of the left, which seems to be a 

 little excavated for the reception of the same ; ligament external, 

 short, rather prominent, and occupjdng an oval or lance-oval 

 shallow cavity, formed by the slight inflection of the margins of 

 the valves immediately behind the beaks ; valves with their margins 

 smooth within and closed all around ; hinge apparently edentu- 

 lous ; surface smooth, with growth-lines and sometimes traces 

 of fine radiating lines ; muscular impressions shallow ; pallial 

 line slightl}' marked, without sinus. 



Differs from Solemj^a in its short gibbous form, want of internal 

 ridge, closed margins, entirely external ligament, ventricose beaks, 

 and their posterior position. 



