BRACHIOPODA. 5 



1888. Spirifera, Calvin. Bull. Laboratory Stale University of Iowa, pp. 19, 28, 



1889. Spirifera, Nbttelroth. Kentucky Fossil Shells, pp. 105-184, pi. vi, vii, viii, ix, x, xi, xii, xiii, 



tigs. 3ti-38 ; pi. xvii, figs. 36-42; pi. xxvi, figs. 2-5; pi. xxi.\, tigs. 13-16, 2'i ; 

 pi. xxxi, figs. 10, 11, 13; pi. xxxii, fi.'rs. 28-31 ; pi. xxxiii, fig.-^. 2:'„ 24. 

 1889. Spirifer, Beechbr and Clarke. Memoirs N. Y State Museum, pp. 75, 77, pi. vi, tigs. 1-7, 9-11. 



1889. Spirifera, Whiteaves. Contributions to Canadian PalEeontology, vol. i, p, 114, pi. xv, fig. 3. 



1890. Spirifera, Wohthen. Geol. Survey of Illinois, vol. viii, p. 105, pi. xi, fig. 5. 



1890. Spirifera, Foekstb. Proc. Boston Soc. Nat. Hist., vol. xxiv, p. 313, pi. v, figs. 5, 6. 



1890. Spirifera, Williams. Bull. Geol. Soc. America, vol. i, p. 491, pi. xii, figs. 12, 13. 



1890. Spirifera, Hall. Bull. Geol. Soc. America, vol. 1, p. 567. 



1890. Spirifera, Hall. Ninth Ann. Rept. N. Y. State Geologist, p. 9. 



1891. Spirifei-a, Hebrick. Bull. Geol. Soc. America, vol. ii, p. 45, pi. 1, fig. 18. 



Shells transversely elongate, rarely produced axially ; with or without me- 

 dian fold and sinus. Hinge-line straight, usually forming the greatest diameter 

 of the shell, but in some of the subdivisions of the genus, short and inconspicu- 

 ous. Cardinal extremities alate, acuminate or rounded. 



Surface covered with granulations, striae, plications or costse, variously 

 grouped and which may be present or absent on the median fold and sinus ; 

 these are crossed by concentric growth-lines which may take the form of 

 varices or expanded lamellag, or be modified into fimbriaj of simple or compound 

 spines. In the subgenera Martinia and Martiniopsis the surface is smooth 

 except for the concentric striae. Shell substance fibrous, impunctate except as 

 below described ; in the smooth species the epidermal layer is minutely pitted. 



The pedicle-valve has the umbo more or less elevated over the hinge-line, 

 the apex acute, erect or incurved. The cardinal slopes show a slight tendency 

 to concavity or excavation, and the median portion of the valve is more or less 

 strongly depressed by a sinus. The cardinal area is broad, flat or incurved and 

 its surface is transversely striated ; the inner shell-layers bear a series of longi- 

 tudinal or vertical canals at whose marginal extremities the fibrous tissue is 

 produced into a row of denticles, corresponding to a row of pits on the opposite 

 valve ; thus forming an accessory articulation of the valves. The essential 

 articulation is effected by means of stout, simple teeth lying at the marginal 

 extremities of the triangular deltidium and supported by dental plates which 

 are usually short, but, in rare types, may be produced even to the anterior mar- 

 gin of the valve The pedicle-passage or delthyrium is usually open. Nor- 

 mally it is closed by a pair of deltidial plates having the form of scalene tri- 



