110 MISSISSIPPIAN BRACHIOPODA 



interpreted and may consequently be assumed as the type of that species. 

 The specimen incorrectly interpreted by Miller belongs to the hitherto 

 undefined species here described. This species resembles both P. bur- 

 lingtonensis and P. fernglenensis in some respects, but is clearly distinct 

 from either. It can at once be distinguished from P. fernglenensis by its 

 somewhat coarser costas, by the entire absence of mesial sinus, by the 

 distinctly flaring lateral and anterior margins, and by the more or less 

 interrupted intercostal furrows towards the beak of the brachial valve. 

 Tn the last character the species resembles P. blairi, but in that species 

 the interruption of the intercostal furrows continues throughout the 

 entire valve, they being essentially absent altogether towards the beak. 

 Horizon. Chouteau limestone . 



PRODUCTUS BLAIRI Miller 

 Plate XIV, Figs. 14-21 



1891. Productus ~blairi Miller, Adv. Sheets 17th Rep. Geol. Surv. Ind., 



p. 79, pi. 13, fig. 16 (not fig. 17). 



1892. Productus Uairi Miller, 17th Rep. Geol. Surv. Ind., p. 689, pi. 13, 



fig. 16 (not fig. 17). 



Description. Shell of medium size or smaller, wider than long, the 

 hinge-line shorter than the greatest width, the greatest width at about the 

 mid-length. The dimensions of a nearly complete specimen are; length 

 from hinge-line to anterior margin 20 mm., length from umbonal region 

 to anterior margin 22.4 mm., greatest width 25.2 mm., length of hinge-line 

 21 mm., convexity of pedicle valve +12 mm., depth of visceral cavity 

 between the two valves 10 mm. 



Pedicle valve strongly convex in mature specimens, the umbonal 

 region rather broad and moderately produced beyond the hinge-line, the 

 surface arched from the umbonal region to the front, the median portion 

 of the valve rather broadly flattened with the lateral slopes curving more 

 abruptly to the lateral margins, the auriculations of moderate size, rather 

 sharply differentiated and distinctly compressed horizontally; mesial 

 sinus very shallow, rather broad and ill-defined, originating in the um- 

 bonal region; beak small, strongly incurved. Surface marked by strong, 

 radiating costse which are interrupted upon the posterior slope of the 

 valve and to some extent anteriorly, so as to appear as series of elongate 

 nodes ; the posterior half of the valve is crossed by strong, concentric, 

 wrinkle-like markings which become more conspicuous towards the car- 

 dinal auriculations; fine concentric lines of growth also cover the entire 

 surface of the valve when it is well preserved. Spine bases not conspicu- 

 ous unless the node-like interrupted portions of the radiating costas each 

 bore a spine, as is perhaps the case. 



