41 
Remarks. This form is most closely allied to Productus sampsoni 
Weller from the Kinderhook of Missouri. It is, however, proportionately 
narrower, with a greater convexity and shorter hinge-line, with a more 
abrupt curvature from the median line of the pedicle valve to its lateral 
margins, and with much more numerous spines (Weller’s species has 
usually only two or three spines upon each side of the beak, whereas the 
radiating costse apparently continue to the beak). 
In surface markings the young shell is a Productellaj but it rapidly 
attains definite costse which, in the absence of a knowledge of internal 
characters, place this shell in the genus Productus. 
Locality and Horizon. The nearest ally occurs in the Lower Missis- 
sippian of Missouri. In the Minnewanka region in the Lower Mississippian 
of section 2-25 (C). 
Productus arcuaius Hall 
1858. Productus arcuaius Hall, Geol. Iowa, pt. 2, p. 518, PI. 7, figs. 4a-b; 
Productella arcuata Hall and Clarke, 1892, Pal. N.Y., vol. 8, pt. 1, 
PI. 17, figs. 31, 32; Productus arcuaius Weller, 1914, Geol. Surv., 
Illinois, Mon. 1, p. 107, PI. 13, figs. 1-8, ? 9-12. 
Remarks. Our form agrees with description and figures of this species 
given by Weller. The only doubtful feature is the hinge-line, which is 
destroyed, but there is some evidence that the surface of the ears was 
“more nearly vertical than horizontal” as in P. arcuatus. 
Locality and Horizon. In the Mississippian of the Mississippi valley. 
In the Minnewanka region in the Mississippian of section 4-3 (R). 
Productus burlingtonensis Hall 
1858. Productus flemingi var. burlingtonensis Hall, Geol. Iowa, vol. 1, 
pt. 2, p. 598, PI. 12, figs. 3a-g; Hall and Whitfield, 1887, King's 
U.S. Geol. Expl. 40th Par., 4, p. 265, PL 5, figs. 9-12; Hall, 1883, 
Rept. N.Y. State Geol. for 1882, PI. (18) 49, figs. 6-8; Hall and 
Clarke, 1892, Pal. N.Y. vol. 8, pt. 1, PI. 18, figs. 6-8; P. burling- 
tonensis Keyes, 1894, Mo. Geol. Surv., vol. 5, p. 41; Weller, 1914, 
111. Geol. Surv., Mon. 1, p. 104, PI. 9, figs. 1-10. 
Remarks. It is at times difficult to distinguish this species from P. 
fernglenensis; the latter species, however, has typically a more strongly 
incurved pedicle valve and the median sinus and fold are absent, repre- 
sented by a mere flattening along the median line of the shell. P. inflatus 
McChesney has more conspicuous ears of the pedicle valve and a narrower 
and deeper median sinus. 
Locality and Horizon . Lower Mississippian (Burlington) of the 
Mississippi valley. In the Minnewanka region in the Lower Mississippian 
of section 2-23 (r), 25 (r), 29 (r). 
