PI>ATE X^^IA— Continued. 



Productus (Mahginifera) Lasallensis, Worthen. 



Ki^. 13. The iiilurioi- of a bracliial valve ; showiiijf the chaiaiiler of tlie iiilenial ridge (z), dietinguiahiiig the 

 subgenu.s Mahginifera. In this species pr(>l)ably occurs the most extreme develoiiment of this 

 feature among- tlie American proiliictids. X 2. 



Uppei- Carboniferous. La Salle, Illhm'ifi. 



Productus magnus, Meek ami Worthen. 



Mg. 15. A much flattened pedicle-valve ; showing the original lengtli of the spines about tlie margins. 

 Keokuk group. Crawfordsville, Indiana. 



Productus semireticulatus, Martin. 



Kig. IH. A portion of the interior of a brachial valve enlarged to show the structure of the brachial ridges, 

 X 3. 



Upper Carboniferous. Perry comity, 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, McChe.sney. 



Fig. 19. Postei'ior view of the cardinal process ; showing its great elevation and strongly tripartite division, 

 the middle lobe being produi'ed 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 irregulai' clusters of fine granules, which 

 become more widely scattered in the centi'al region about the median septum. The origin of 

 this structure, as well as that seen in figures 16 and 18, has not been ascertaineil. X 2. 

 Upper Coal Measures. Near Katisas City, Missouri. 



Productus punctatus, Martin. 



(See Plate XIX, tigs. 14-lB.) 

 Fig. 21. The interior of a brachial valve of a vei-y large and finely preserved specimen. The cardin.al pro- 

 cess shows the coalescence of the inner ajiophyses, the deep median groove on its surface indi- 

 cating the original division into two lobes. The mascular impre.ssions 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 Kaii-ia/t City, Missouri. 



Productus .^quicostatus, Shunuird. 



Figs. 22, 23. Two views of a specimen from which the upper or visceral portion of the pedicle-valve la 

 bi'oken, exposing the flattened surface of the lower valve. These figures are inti-oduced to show 

 the jjcculiar mode of growth of the shell on the anterior margin, a tendency frequently exhib- 

 ited by the Striati, and which, in its exti-enie development, results in an enfolded exi)ansion oi- 

 complete tube, as in P. probo.scideus (Proboscidella). 

 Coal Measures. Nel/i-aska. 



Productus ( ? auriculatus, Swallow.) 



Fig. 24. The extei-ior of a (ledicle-valve, the surface of which is tVee of spines except along the cardinal 

 margin. 



Coal Measures. Near Kaiuias City, Missouri. 



Genus STROPHALOSIA, King. 

 Strophalosia SPONDYLIFORmis, While and St. John. 



Figs. 2,">, 2(3. Opposite sides of a sjiecimen ; showing the cardinal areas, deltidia and scar of attachmeut. 

 Coal Measures. Missouri. 



