Mytilidae S3 



Brachidontes citrinus'" (Roding) PI. 7, fig. 38 



Alt., 14; length, 38 mm. The shape resembles B. exustus, is 

 larger and more slender; bluish gray covered with bright yellow 

 epidermis; surface ribbed, smooth anteriorly; umbos small, round, 

 incurved; interior white, stained with purple; margins smooth, epider- 

 mis reflected internally. 



Not ordmanly found on the beaches. Dredged in three to 

 six fathoms. 



Genus 310I)I0LUS Lamarck, 1799* 



Slodiolns^" americaiins (Leach) (M. tulipus Linne) PL 7, fig, 36 



Alt., 33; length, 65 mm. Shell moderately thick, translucent, 

 smooth except for incremental lines; color brown or yellowish brown, 

 with red undertone; epidermis glossy brown, shaggy toward post- 

 erior end; umbos anterior, incurved, closely approximate, not ter- 

 minal; shell inflated, slightly carinate above, a shallow sulcus below; 

 interior pink near umbos, purple, nacreous; epidermis reflected over 

 smooth margms. 



This is a nest building species. Common on Gulf beach, dredged 

 in three to seven fathoms. 



Modiolus demissus*"^ granosissimus (Sowerby) PI. 7, fig. 37 



Alt., 30; length, 65 mm. Shell brown with thin brown epidermis; 

 sculpture of fine ribs cut transversely into granules; lower anterior 

 portion of valves smooth; umbos inconspicuous, anterior, not 

 terminal, often eroded through to nacreous layer; hinge margin 

 slightly convex, other margins slightly rounded; byssal opening be- 

 low; interior purple, nacreous, margins crenate. 



A shallow water species, often found on oyster bars. 



Subgenus AMYGDALUM ^s Megerle von Miihlfeld, ISll 

 3Iodiolas papyria^^ (Conrad) {Mytilus arbor escens Dillwyn) PI. 7, fig. 39 



Alt., 8; length, 22 mm. Shell fragile, smooth, polished, and 

 iridescent greenish color; thin, transparent epidermis; inconspicuous 



*^ Lat., Modiolus, a small measure. 



*" Lat., demittire, to send away; granosus, full of grains. 

 *^ F., citrine, yellow, from Lat., citrus, citron tree. 

 ** Lat., amygdalum, an almond. 

 ^^ Lat., papyrus, paper. 



*Opin. 325, Int. Rules-Zool. Nomen., Jan. 7, 1955, Modiolus Lam., 1799, is 

 validated and Volsella Scopoli, 1777 is suppressed. 



