154 AMERICAN JOURNAL 



the hinge plate, and a prominent cardinal process 

 fitting into a semilunar pit below the neural 

 area. Each valve bearing a tubular process on 

 each side of the septum. 



LlNGHJLEPis. — Visceral area neurally tripartite, hsemally 

 flabelliform ; post. occl. scars within the visceral 

 area ; ant. add. in its anterior sinuses, ant. occl. 

 median. 

 OBOLIN^. — Post adductor scars double, more or less 

 separated from the median line. Shell more or 

 less orbicular. 



Obolus. — Shell orbicular ; neural beak short ; hinge 

 margin flat ; cardinal border grooved for the ped- 

 icels. Haemal beak inconspicuous, valve more or 

 less flattened. Ant. add. scars ovate, converging 

 anteriorly. 



Obolella. — Shell with minute area usually grooved. 

 Ant. add. scars diverging anteriorly. 

 Kutorgina. — Hinge line straight, meeting tlie lateral mar- 

 gins at an angle. Neural valve with an area and 

 foramen. Shell Orthisiniform. 

 Monoholina. — Shell like Obolus, muscular impressions 

 united along the median line. 



?Spondylobus. — Shell suborbicular. Haemal apex excen- 

 tric. Valve with a thickened base interiorly. Neural 

 valve with a marginal apex, channelled, and with 

 a thickened hinge line on each side of the groove. 

 Shell structure testaceous, not glossy, fibrous. 



Family LINGULID.E, King. 



Lingulidce, Dav., Int. Br. Brach. p. 133. 



Shell furnished with a peduncle passing between the apices of 

 the valves; inarticulated, subequivalve, composed of horny laminae 

 alternating with cretaceous layers ; containing phosphate of 

 lime ; impunctate. Brachia unsupported by calcified processes. 



Section LINGULIN^E. 



Genus LTNGULA, Brug. 



Lingula, Brug., Ency. Meth. tab. 250, 1789. 

 Fharetra, Mus. Bolt. Ed. ii, p. Ill, 1819. 



Shell thin, subequivalve, equilateral, tapering at the beaks, 

 expanded at the pallial region. Valves held together by the 

 adductor and pedicel muscles. Beak of the neural valve slightly 



