106 MISSISSIPPIAN BRACHIOPODA 



auricular extensions of the pedicle valve, and the presence of a mesial 

 sinus. Th auricular extensions of the shell are usually more or less 

 imperfectly preserved and oftentimes appear to be essentially wanting, 

 and in such examples the hinge-line is apparently shorter than the great- 

 est width as stated by Hall in the original definition of the species, 

 but in all specimens examined in which the auricular extensions are 

 completely preserved, the hinge-line is longer than the width of the shell 

 anteriorly. The species most closely resembles P. inflatus, but in that 

 species the auricular extensions are somewhat more conspicuous, the 

 mesial sinus is usually narrower and deeper, and the semireticulate 

 markings of the posterior portion of the pedicle valve are much less 

 conspicuous. 



Horizon. Burlington limestone. 



PRODUCTUS FERNGLENENSIS "Weller 

 Plate IX, Figs. 11-17 



1909. Producing fernglenensis Weller, Bull. Geol. Soc. Am., vol. 20, 

 p. 299, pi. 12, figs. 14-17. 



Description. Shell of medium size or a little larger, wider than lon^ 

 in most specimens, but sometimes becoming longer than wide in old 

 examples, hinge-line a little shorter than the greatest width, the anterior 

 margin regularly rounded or sometimes a little sinuate in the middle. 

 The dimensions of an incomplete specimen are : length from hinge-line 

 to front margin 21.3 mm., length from umbonal region to front margin 

 27 mm., length of hinge-line 27.5 mm., greatest width 33.5 mm., convexity 

 of pedicle valve 23 mm. The largest specimen observed has a length of 

 39 mm. from the umbonal region to the front margin, with a width of 

 35 mm. 



Pedicle valve gibbous, the umbonal region broadly pointed towards 

 the beak and strongly protuberant beyond the hinge-line, the mesial 

 portion of the valve broadly flattened from the umbonal region to the 

 front, the surface very gently convex, nearly straight or slightly con- 

 cave transversely, rounding more abruptly into the lateral slopes which 

 drop nearly vertically to the lateral margins, the auriculations small 

 but rather well defined from the lateral slopes; mesial sinus wanting 

 or only slightly depressed, and ill defined laterally; the beak strongly 

 incurved. Surface covered by rounded, radiating costae, usually 1 mm. 

 or less in width, which increase by bifurcation upon the posterior slope, 

 on the anterior slope they either continue without division or sometimes 

 break up into two or more in front of the spine bases and continue to the 

 front with a fasciculate arrangement, often becoming coalescent near 

 the margin; upon the posterior slope the radiating eostae are crossed by 

 rather conspicuous, concentric, wrinkle-like markings which are com- 



