181 



C---> 



h 



Fig. 78. Diagram of Spirifer. ( A. B^ Longitudi- 

 nal axis marlving the height ; iC, D) Tran.sverse axis 

 marking the width : ( JB ) anterioi- ( front ) end ; (^-1 ) pos- 

 terior or beak end ; ( ar. i cardinal area : ( b ) beak 

 ( or umbo » ; (Br.) brachial valve ; ( car. sZ.) cardinal 

 slopes : ( ce ) cardinal extremities ; (del.) delthyriura ; 

 ( fd. ) mesial fold (if brachial valve : ( hy. ) hinge-line ; 

 CPed.) pedicle valve : (pi.) plications; (si.) mesial 

 sinus of pedicle valve. cOrigiual.) 



The important surface features of tlie shell are: the lines of growth, 

 the VAflvAimg plicattuns or striatioiis, the fold or medial elevation, and the 

 sinus or medial depression, the fold commonly occurring in the brachial, 

 and the sinus in the pedicle, valve. 



The following diagram represents the principal features of the shell, 

 and gives its orientation. 



Note. — For an account 

 of the anatomy of the ani- 

 mal, any textbook of 

 zoology may be consulted. 

 Zittel's text-book of PaliV- 

 ontology (Eastman's trans- 

 lation) is standard. For 

 the best account of the 

 animal and the shell, as 

 well as detailed descrip- 

 tions of the genera, the 

 student is referred to the 

 admirable hand-book of 

 the Brachiopoda, by Hall 

 and Clarke, entitled ' ' An 

 introduction to the study 

 of the Brachiopoda," and 

 published in the reports of 

 the State Geologist of New York, for 1891 and 1893. Vol. VIII., Pts. I. 

 and II., of the Paleontology of New York, should also be within the reach 

 of the student. 



The specific descriptions will nearly all be found in Vol. IV. of the 

 Palaeontology of New York, and for a more detailed study that volume 

 should be consulted. For classification, synonomy, and distribution 

 consult "A Synopsis of American Fossil Brachiopoda," by Charles 

 Sclmchert. Bull. 87, U. S. G. S. In the preparation of the following 

 brief descriptions the above-named sources have largely been draw'n 

 upon. 



BRACHIOPODA INARTICULATA. 

 Genus LINGULA. BKr(4UiERE. 



[Ety. : Lingula, a little tongue.] 



(1789: Hist. Natur. des Vers Testaces. 1892: Pal. N. Y., 

 Vol. VIII., Pt. I., p. 2.) 



Shell with the valve.^ nearly equal, and varying- in outline 

 from elongate-ovate to sub-triangular, always longer than 

 wide. Valves arched. Animal attached by a long, muscular 

 pedicle, which protrudes from between the beaks of the two 

 valves. 



