PLATE XVnA— Continuea. 



Productus (Makginifera) Lasallensis, Worthen. 



Fig. 13. The interioi' of a Vjracliial valve ; showing- the character of the internal i-iilge (z), ilistinguishing the 

 sub-genus MARfiiNiFEKA. In this species probably occurs the most extreme development of this 

 featui-e among the American pi-oductids. X 2. 



Upper Carbonifei'ous. La Salle, Illhwiii. 



Productus magnus, Meek and Wortheii. 



Fig. 15. A much flattened pedicle-valve ; showing the original length of the spines about the margins. 

 Keokuk group. Crawfordsville, Indiana. 



Productus semireticulatus, Maitin. 



Fig. Iti. A jKirtiim of the intei-ior of a brachial valve enlai-ged to show the structure of the bi-achial ridges, 

 X 3. 



Upper Carboniferous. Peiry county, Ohio. 

 Fig. 17. Cardinal vievf of an intei-nal cast of the pedicle-valve ; showing the impressions of the cai-dinal 



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 Measui'es. Newcastle, Ohio. 



Productus symmetricus, McChesiiey. 



fi'i-. 19. Posterior view of the cardinal process ; showing its great elevation and strongly tiiparlite division, 

 the middle lobe being pi'oduced 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 lidges or areas. 

 The surface within the curved ridges is covered with iri-egular 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 figui-es 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 ti-ace of the brachial ridges. 



Upper Coal Measures. Near Kansas City, Missouri. 



Productus ^quicostatus, Shumard. 



Figs. 22, 23. 'J" wo 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. proboscideits (Proboscidblla). 

 Coal Measures. Nebraska. 



Productus ( ? auriculatus, Swallow.) 



Fig. 24. The exterior of a jiedicle-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. 



