PLATE XVIIa—C ontinued. 
Productus (Marginifera) Lasallensis, Worthen. 
Fig-. 13. The interim* of a brachial valve; showing the character of the internal ridge (z), distinguishing the 
sub-genus Makginifera. In this species probably occurs the most extreme development of this 
feature among the American productids. X 2. 
Upper Carboniferous. La Salle, Illinois. 
Productus magnus, Meek and Worthen. 
Fig. 15. A much flattened pedicle-valve ; showing the original length of the spines about the margins. 
Keokuk group. Crawfordsville, Indiana. 
Productus semireticulatus, Martin. 
Fig. 16. A portion of the interior of a brachial valve enlarged to show the structure of the brachial ridges, 
X 3. 
Upper Carboniferous. Perry county, Ohio. 
Fig. 17. Cardinal view of an internal cast of the pedicle-valve ; showing the impressions of the cardinal 
area, the posterior and anterior adductor and the diductor muscles. 
Fig. 18. The interior of a brachial valve, drawn from a gutta-percha impression of an internal cast; showing 
the muscular scars and the peculiar structure of-the brachial areas. 
Coal Measures. Newcastle, Ohio. 
Productus symmetricus, McChesney. 
Fig. 19. Posterior view of the cardinal process; showing its great elevation and strongly tripartite division, 
the middle lobe being produced by the coalescence of the inner members of the two principal 
divisions of the process. X 3. 
Fig. 20. A portion of the brachial valve enlarged to show the structure of the brachial ridges or areas. 
The surface within the curved ridges is covered with irregular clusters of fine granules, which 
become more widely scattered in the central region about the median septum. The origin of 
this structure, as well as that seen in figures 16 and 18, has not been ascertained. X 2. 
Upper Coal Measures. Near Kansas City, Missouri. 
Productus punctatus, Martin. 
(See Plate XIX, figs. 14-16.) 
Fig. 21. The interior of a brachial valve of a very large and finely preserved specimen. The cardinal pro¬ 
cess shows the coalescence of the inner apophyses, the deep median groove on its surface indi¬ 
cating the original division into two lobes. The muscular impressions are thickened, strongly 
arborescent, and show a faint division into anterior and posterior scars. Though so well pre¬ 
served, the specimen bears no trace of the brachial ridges. 
Upper Coal Measures. Near Kansas City, Missouri. 
Productus asquicostatus, Shumard. 
Figs. 22, 23. Two views of a specimen from which the upper or visceral portion of the pedicle-valve is 
broken, exposing the flattened surface of the lower valve. These figures are introduced to show 
the peculiar mode of growth of the shell on the anterior margin, a tendency frequently exhib¬ 
ited by the Striati, and which, in its extreme development, results in an enfolded expansion or 
complete tube, as in P. proboscideus (Proboscidella). 
Coal Measures. Nebraska. 
Productus (? auriculatus, Swallow.) 
Fig. 24. The exterior of a pedicle-valve, the surface of which is free of spines except along the cardinal 
margin. 
Coal Measures. Near Kansas City, Missouri. 
Genus STROPHALOSIA, King. 
Strophalosia spondyliformis, White and St. John. 
Figs. 25, 26. Opposite sides of a specimen ; showing the cardinal areas, deltidia and scar of attachment. 
Coal Measures. Missouri. 
