Mactridae 89 



Genus MACTKA Linne, 1767 



Subgenus MACTK0T03rA Ball, 1894 



jractra's* f rag-ills Gmelin PI. 17, fig. 113 



Alt., 35; length, 50 mm.; specimens up to 80 millimeters have 

 been recorded. Shell oval, slightly inequilateral; white, with close, 

 narrow concentric ridges and pale-brown epidermis heaviest over 

 posterior rostration; umbos rounded, almost central; anterior and 

 posterior margins sloping to join rounded ventral margin; rostrate 

 and gaping behind; interior white, rounded pallial sinus, smooth 

 margins. 



Genus SPISULA Gray, 1837 



Subgenus HEMIMACTKA Swainson, 1840 



Spisulsi solidisshna similisi ' ■ (Say) PI. 17, fig. 114 



Alt., 50; length, 70 mm.; specimens have been taken up to 90 

 millimeters. Shell oval; nearly equilateral; smooth, creamy, with 

 thm, glossy, light-brown periostracum which is thicker at posterior 

 and reflected over the free margm; umbos acute, anterior to mid- 

 line; cardinal teeth and hinge fosse typical, lamellar lateral teeth with 

 opposite deep socket; muscular impressions above center of shell; 

 pallial smus short; margins faintly crenate. 



Genus MULINIA Gray, 1837 

 Miillnia lateralis corbuloides^'^' Deshayes PI. 17, fig. 115 



Alt., 11.5; length, 13.5; diam., 6.5 mm. Shell small, trigonal, 

 white, glossy, brownish epidermis; umbos high, inflated; anterior and 

 posterior margins slope abruptly, posterior longer, slightly concave; 

 flat posterior rostration; cardinal and lateral teeth and typical 

 fossette; short, oblique pallial sinus. 



Genus AlVATIIVA Schumacher. 1817 

 Aiuitiiia lineatiii 7 (Say) PI. 18, fig. 116 



Alt., 41; length, 50 mm. Shell, white, thin and fragile; thin, 



^3* Gr., maktra, a kneading trough. 



^■'•' Spisula, probably from Von Spix, German naturalist; Lat., solidus, 



solid ; similii, like. 

 ^5s Lat., mulus, a hybrid animal (?); lateralis, side; corbula, little basket. 

 15^ Lat., anatinus, pertaining to a duck; linea, line. 



