54 University Geological Survey of Kansas. 



sometimes called dorsal valve. This process extends beyond the 

 hinge backward under the beak of the other valve, and when 

 the muscle contracts acts as a lever opening the shell. 



In the front cavity are situated the brachia or arms, as they 

 are called. They are often of coiled or spiral form, supported 

 by horny or calcareous supports which are sometimes preserved 

 in the fossils. These brachia carry a long fringe, which by its 

 vibration keeps a current of water flowing through the shell, 

 from which the animal separates its food. There are no special 

 organs of respiration, which is performed probably by the 

 blood flowing through many thin membranes which are con- 

 stantly in contact with the current of water passing through the 

 shell. The figures on page 53 serve to illustrate the parts of 

 the animal and the muscular impressions found in the shells. 



The full synonymy is given for the species herein described, 

 but not a full bibliography. For a full bibliography, the reader 

 is referred to Mr. Charles Schuchert's work on the North Ameri- 

 can Brachiopoda, Bulletin No. 87 of the United States Geological 

 Survey of 1897. 



LINGULA. 



Bruguiere, Encyc. Metho.. I, p. 250, (1792). 

 Meek and Hayden, Pal. Upp. Mo., p. 63, (1861) ; etc. 



Lingula mytiloides. Plate VIII, fig. 5. 



Lin quia mi/tlloides Sowerby, Min. Coach., i, p. 55, pi. xix, ff. 1, 2, (1813); 



Meek and Hayden, Geol. Surv. 111., v, p. 572, pi. xxv, f. 2, (1873). 

 ? Lingula umbonata Keyes, Geol. Surv. Mo., v, p. 38, pi. xxxv, f. 4, (1895). 



Shell small, elliptical, posterior extremity slightly narrowed ; 

 beak extending to the hinge line, not prominent. Anterior 

 margin broadly rounded, lateral margins subparallel ; the great- 

 est diameter about the middle of the shell. The surface is 

 marked by fine concentric lines of growth. Length, 7 mm. ; 

 breadth, 5 mm. ; larger specimen, length, 11 mm. ; breadth, 

 7 mm. 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Topeka, Burlingame. 



