342 LINGULID^. 



Lingulse existed in the British seas as late as the period of the 

 Coralline Crag. The recent species have been found at small 

 depths, and even at low-water half buried in sand. L. Davisii, 

 Lower Silurian, Tremadoc, has a pedicel-groove like Obolus. 



GLOTTiDiA, Dall, 18t0. Shell with two diverging internal 

 laminae in the neural valve proceeding from the beak, and a 

 mesial septum in the haemal valve ; otherwise like Lingula. 6 

 recent sp. E. and W. coasts of North America. L. albida, 

 Dall. California. 



LINGULELLA, Salter, 1866. {Etym. — Diminutive of Lingula.) 

 " Shell nearl}^ equivalve, broad, oblong, the ventral valve pointed, 

 with a distinct pedicel-groove. Muscular scars strong, nearly 

 as in Obolus, but the pair of anterior retractors are more linear 

 than in Obolus, and the sliding muscles small, and not quite 

 external as in Obolus." — Salter. 3 sp. Cambrian, Lower Sil- 

 urian ; Ireland, Wales, Norwa3\ L. Damsii,WQoy. 



LiNGULEPis, Hall, 1863. (Etym. — Lingula., a little tongue; 

 lepis^ a scale. ) Shell thin, subovate, or subtrigonal ; composition 

 and structure as in Lingula. Ventral or larger valve with beak 

 more or less produced and pointed ; visceral scar trilobed, with 

 a longitudinal raised mesial line or septum — lateral divisions 

 diverging, and usually longer than the middle one ; dorsal or 

 smaller valve with the beak less produced than that of the other; 

 visceral scar flabelliform. 4 sp. Cambrian ; America. L. pin- 

 mformis, Owen. 



DiGNOMiA, Hall, 1873. With strong internal median septum, 

 otherwise as in Lingula. Silurian — Devonian ; U. S. L. alveata. 

 Hall. 



