158 • Trans. Acad. Sci. of St. Louis. 



In his original description White recorded this species 

 from most of the beds of the Kinderhook at Burlington. 

 The types, however, are without exception from bed No. 

 4, and the rhynchonelloid shells from other beds do not 

 possess characters which seem to warrant their specific 

 identity with these. 



Stringothyris halli Win. 



PI. XIII. f. 1-3. 



Original description. "Shell of medium size, trans- 

 versely elongate, widest along the hinge-line; greatest depth 

 of the two valves equalling or exceeding the greatest length. 

 Pedicle valve with a deep, defined sinus; beak very elevated ; 

 surface sloping thence with but little convexity, to all parts 

 of the margin, — being sometimes even concave between the 

 apex and the cardinal extremities; area large, triangular, 

 transversely striate, flat or slightly arched, with a more 

 marked incurvation just beneath the beak; perforated by a 

 narrow, or moderately wide, triangular fissure, which is 

 grooved along its lateral borders as if for the reception of a 

 deltidium ; dental plates rather short, diverging at an angle 

 of 66°; mesial septum a low ridge extending two-fifths the 

 length of the valve ; line of divaricator scars extending with 

 a curve from the inner end of dental plates to inner end 

 of mesial septum. Brachial valve moderately ventricose, 

 with a convex surface, and abrupt well-defined mesial eleva- 

 tion, and a small beak which overhangs the base of the fissure 

 in the area of the opposite valve, — the area being scarcely 

 perceptible in the brachial valve Surface ornamented by 12 

 to 16 rounded ribs on each side of the mesial fold and sinus, 

 becoming obsolete toward the lateral angles. Mesial fold and 

 sinus destitute of ribs. The whole surface is further marked 

 by faint, delicate lines of growth." 



" Length of hinge-line 33 mm.; depth from beak of pedi- 

 cle valve to most prominent point of brachial — which is 

 nearly at right angles to the plane of the valves — 17i mm. ; 

 distance from hinge-line to middle of anterior margin 13| 

 mm.; elevation of area 12 mm.; width of fissure at base 

 7 mm." 



