Strophomena and Other Fossils 
81 
JudgiDg from the fact that Strophomena planumbona makes its 
appearance earlier in the Waynesville section in Ohio and Indi- 
ana than southward in Kentucky, it is regarded as another of 
the species having a northern or northwestern origin as far as 
the immediate territory under consideration is concerned. It 
evidently is closely related to species distributed from Illinois 
southward as far as southern Tennessee. The connection with 
this western basin, however, appears to have been by way of 
northern Illinois rather than by means of some more southern 
channel. This leaves the general question as to the origin of 
the Mississippi Valley Richmond entirely untouched. 
Strophomena planumbona-elongata, James 
{Plate IV, Figs, 1 A-L; Plate IX, Figs. 4 A, B) 
The types of Strophomena elongata, James, numbered 510, are 
preserved in the James collection, in the Walker Museum, at 
Chicago University. 
The types present the following characteristics. General out- 
line of the shell broadly semicircular, elongate along the hinge- 
line. Angle between the general lateral outline and the hinge- 
line between 60 and 70 degrees. Brachial valve convex, especi- 
ally from front to rear; the transverse section much less convex, 
moderately flattened toward the beak, especially over an area 
extending 8 to 10 mm. from the posterior margin. Usually an 
almost imperceptible median depression extends forward from 
the beak about 6 or 7 mm. Radiating striae of the brachial 
valve subequal and of medium size, about 14 or 15 in a width of 
5 mm. Radiating striae of pedicel valve slightly finer, about 
16 or 17 or 18 in a width of 5 mm. at 20 mm. from the beak. 
Greatest convexity of the pedicel valve near the middle or slightly 
anterior. Hinge-area of medium height, narrowing toward the 
extremities, equalling 2.8 mm. at the beak. 
Width of one of the type specimens, 35 mm.; length 22 mm.; 
convexity at 11 mm. from the beak, 8 mm. Length of the hinge- 
area, 34 mm.; height at the beak, 2.8 mm. Maximum convexity 
of the hinge-area, observed among other type specimens, 4.4 
mm., in a shell 38 mm. wide along the hinge-line, 23.5 mm. long, 
and with a convexity of 13 mm. This was a very obese specimen. 
Cincinnati Quarterly Journal of Science, vol. i, p. 240, 1874. 
