PLATE XVITa— Continued. 



Productus (Makginifera) Lasallensis, Woithen. 



Vig. 13. The iiiterioi- of a brachial valve ; showiiif,'' the chaiuotci- iif the iiilenial ridge {z), disting-uisUiutj the 

 sub-genus Maucinikeha. In this specie's probably occurs the most extreme development of this 

 feature among (he American pi-oiluctiils. X 2. 



Upper Carboniferous. La Salle, Illinoit. 



Productus magnus, Meek :iih1 Wortheii. 



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

 Keokuk group. Crawfordsville, Indiana. 



Productus semireticulatus, Miirtin. 



Fig. 1«. A jxirtion of the interior of a brachial valve enlarged to show the structure of the bi-achial ridges, 

 X 3. 



Upper Carboniferous. Pe}fy county, Ohio. 

 Fig. 17. Cardinal view of an internal cast of the pedicle-valve; showing the impres-sirns of the cardinal 



area, the posterior and iinterior adductor and the <liductor muscles. 

 FiL'. IS. 'I'he inteiior of a brachial valve, diawn from a gutta-percha impression of an internal cast ; showing 

 the muscular scars and the peculiar structure of the brachial ai-eas. • " i 



Coal Measures. Newcastle, Ohio. 



Productus stmmetricus, McCheriiiey. 



Kig. 19. Posterior view of the cardinal ]irocess ; -showing its gi-eat elevation and strongly lri|iarlite divisio:i, 

 the middle lobe being produced by the coalescence of tlie inner members of the two principal 

 divisions of the. process. X 3. 



Fig. 20. A poi'tion 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 clustei-s of tine grannies, which 

 become more widely scattered in the central region about tlie median sejitum. The origin of 

 this structure, as well a.s that seen in figures 10 and 18, has not been ascertained. X 2. 

 Upper Coal Measures. Near Kansas City, Missonri. 



Productus punctatus, Mart in. 



(See Plate XIX, figs. 14-1(3.) 

 Fig. 21. The intei-ior of a brachial valve of a very large and finely preserved specimen. The cardinal pro- 

 (•CS8 .shows the coalescence of the inner apophy.ses, the deep median groove on its surface indi- 

 cating the original division into two lobes. The muscular impressions are thickened, strongly 

 arbore.scent, and show a faint division into anterior and posterior scars. Though so well pre- 

 served, the specimen bears no trace of the bractiial ridges. 



Upper Coal Measures. iVi?f(r Kan.ia.<! City. Mi.i.iouri. 



Productus .siquicostatus, Shuiuard. 



Figs. 22, 23. 'l"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 antei'ior margin, a tendeni:y frequently exhib- 

 ited by the jStriatl, and which, in its extreme development, results in an enfohled expansion or 

 complete tube, as in P. probo.icideus (Proboscidklla). 

 Coal Measures. Nebraska. 



Productus ( ? auriculatus, Swallow.) 



Fig. 24. The exterior of a pedicle-valve, the surface of whicdi is free of spines except along the cardinal 

 margin. 



Coal Measures. Near Katisas City, Missouri. 



Genus STROPHALOSIA, King. 

 Strophalosia spondyliformis, VVliiU- and St. John. 



Figs. 20, 20. Opposite sides of a specimen ; showing the cardinal areas, deltidia and scar of attiichmeut. 

 Coal Measures. Missouri. 



