372 I'rocccduujs of the O/iin SUttc .Ictidcmy of Science. 



marked by line radiating plications which are crossed ])y promi- 

 nent concentric wrinkles in both the aurictilar and umbonal 

 regions. 



Length 43 mm.; wicUh 30 mm.; hinge line 16-20 mm. 



The shell is characterized l)y its fragile nature, tine pli- 

 cations, and trumpet-shaped aperture. The umbonal half of the 

 pedicle valve is, in most specimens, broken away, leaving the 

 interior surface of the umbonal half of the brachial valve and 

 the outer surface of the anterior half of the pedicle valve ex- 

 posed, seemingly as one valve (Fig. 8b). 



The specimen that Whitfield figured was undoubtedly an 

 imperfect one. The shell must have been so broken that the 

 ventral view showed the umbonal half of the brachial valve and 

 the anterior half of the pedicle valve. And, furthermore, the 

 •expanded, anterior margin was evidently broken away. As a 

 result of this imperfection, the pedicle valves of the Alaxville 

 specimens resemble Hall's figures of P. tenuicostns (Geol. vSurv. 

 Iowa, \^ol. I, pi. 24, fig. 2 a-c), whereas the brachial valves agree 

 with Whitfield's figures. The shell dififers, though, from P. 

 tenuicostns in that the beak of the pedicle valve is more pointed, 

 in that the transverse section is roitnded instead of subquadrate, 

 and in that the umbonal half of the brachial valve is slightly 

 •concave rather than flat. The hinge line of P. pileifonnis, also, 

 varies from 16 to 20 mm. whereas the one of the only specimen 

 used by Hall is 23 mm. 



Horizon and locality. — Maxville limestone. 

 Upper zone : Mouth of Buckeye Fork, Fultonham ; Gladstone 



Mills, Thompson Residence (aa), below Thompson Resi- 

 dence, White Cottage. 

 Lower zone : Cut No. 4, Mt. Perry-Fultonham ; Folk Quarry, 



Rtishville. 



PRODUCTUS CESTRIENSIS-Worthen. 

 1855. Productns elegans. Norwood and Pratten, Jour. Acad. Nat. Sci. 

 Phil. (2), Vol. Ill, p. 3, pi. 1, figs. 7a-c. (Not P. elegans 

 McCoy). 

 Mountain limestone: Chester and Kaskaskia, Illinois; near Hat 

 Island, Missouri. 



