The ISTew Species of Beachiopoda. 331 



edge, slopiDg rather abruptly backward. Its surface bears the 

 usual tripartite arrangement of the muscular scars. Anterior 

 longitudinal septum distinct. From directly behind the crescent 

 to the central muscular impressions is a very broad, smooth, 

 lunate slope, occupying the position of the simple umbonal cavity 

 usual in this valve of Monomerella., and presenting the appear- 

 ance of an abnormal deposition or callosity. 



Though represented by a single specimen only^ this form shows 

 features not elsewhere observed in the genus, viz., the great 

 development of the cardinal area, the composite character of the 

 muscular impressions terminating the crescent, and the broad 

 posterior slope. 



From the Niagara group. Near Grafton^ Wisconsin, 



Rhinobolus Davidsoni. 



Plate 2, figs. 6-8. 



Rhinobolus Davidsoni, Hall. Palaeontology of N. Y., toI. VIII, pt. 1, p. 176, 

 pi. iv b, figs. 10-12. 1892. 



Shell with a circular outline, except for the prominence of the 

 beak. Pedicle- valve with a moderately high, acuminate cardinal 

 area, upon which the central area, the deltidial ridges and areal 

 borders have each about the same width. Cardinal slope short; 

 crescent sharply defined ; terminal scars distinct. Platform 

 broadly Y-shaped, sloping less abruptly backward than in JR, 

 Galtensis. Pallia! sinuses faint. Brachial valve with marginal 

 beak and inconspicuous area. Crescent more prominently devel- 

 oped than in the opposite valve, transverse over the crown as in 

 DiNOBoLus ; terminal scars large. Platform more sharply angu- 

 lated than in the pedicle-valve and somewhat more elevated, 

 bearing conspicuous lateral and anterior scars. Longitudinal 

 septum not pronounced. Pallial sinuses quite distinct. 



This species is based upon internal casts of opposite valves, 

 which are in entire harmony with each other and are readily sepa- 

 rated from Dinobolus Conradi and the various species of Mono- 

 MERELLA. associatcd with them at the same locality. It is distin- 

 guished from the forms referred to Rhinobolus Galtensis^ Bil- 

 lings, by its more circular outline, less elevated pedicle-umbo, 

 inconspicuous brachial umbo, and broader, though less sharply 

 elevated platform. 



Niagara group. Near Grafton^ Wisconsin. 



