PALEONTOLOGY OF THE UPPER MISSOURI. 



SILURIAN AGE, 



(POTSDAM OE rSlMOBDIAL PEKIOD.) 



MOLLUSCA. 



CLASS BRACHIOPODA. 



FAMILY LINGULID^E. 



Shell subcqnivalvc, hingeless, oblong, oval, subtrigonal, or suborbicu- 

 lar. covered with a corneous epidermis ; texture subcorneous or testaceous; 

 structure laminated and minutely tubular or more or less compact; in- 

 terior without calcified spiral or loop-like appendages. 



Animal with elongated fleshy, subspiral oral arms, situated on each 

 si (It; of the mouth, and fringed with numerous cirrhi; attached by a thick 

 peduncle passing out between the beaks of the valves; mantle highly 

 vascular, and iViuirnl with corneous Betas. 



This family includes the four known genera, Lingula, Lingulepia, O&oZtw, and 

 Ol,,,l, II, i Y It was introduced at the dawn of the Silurian age, and is represented in 

 all the succeeding formations, as well as in our existing seas. 



Genus LINGULEPIS, HALL. 



Sgno*. Linyula (sp.), Owns, Report Wisconsin, Iowa and Minnesota, 1852, p. 583 ; HALL, Poster & Whitney's Report 

 Lake Sup. part ti, 1851 , p. 204 ; MKEK & HATDRH, Proceed. Acad. Phila. 1858, p. 49 (not Liayula, BBD.I. 1792). 

 /.iMi/M/./iin, HALL, Sixteenth Ann. Kept. Regents' University , N. Y., 1863, p. 129. 

 Elym. Lingulii, a little tongue ; Xwrtc, a scale. 

 Type.Lingula pinmiformll, Own. 



Shell thin, subovate, or subtrigonal ; composition and stnicture as in LinguJa. 

 Ventral or larger valve with beak more or less produced and pointed ; visceral 

 scar trilobate, 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 flabclliform. 



The above description is mainly as given by the author of the genus, excepting 

 that we have described the markings seen within the valves as visceral scars instead 

 of muscular impressions, and left out a few such characters as " inequivalve, equi- 

 lateral," &c., which being common to all the genera of the family, and indeed normally 

 characteristic of the whole class, need not be repeated in a generic description. We 



1 February. 1804. ( 1 ) 



