Welter — Kinderhook Fmmal Studies. 17 



less imperfectly preserved, mo that a complete description of 

 them cannot be given. In general form they seem to resem- 

 ble C. tumidus Herrick, from the Waverly group of Ohio, 

 more closely than any other species, though they apparently 

 have a smaller number of radiating plications than fifty, the 

 number given for that species. It is possible that with suffi- 

 ciently well-preserved specimens, these shells would be found 

 to belong to an undescribed species, but for the present they 

 will be compared with C . tumidus. 



Productella conckntrica Hall.? 



A single imperfect specimen of the interior of the brachial 

 valve of a Productella is identified with some doubt as P. con- 

 centrica. It differs from Hall's * illustration of this species 

 chiefly in its greater size, the breadth being about 23 mm. 

 while the figure of P. concentrica is only a little more than 

 12 mm. wide. Aside from the difference in size there seem 

 to be no essential differences between the two shells, 



Productus sp. 



Several fragments of a species of this genus are present in 

 the North view collection, but their condition of preservation 

 is not such as to allow of their specific identification. The best 

 preserved specimen, and perhaps also the others, is of the 

 type of P. cora, and it is possible that it should be identified 

 with P. laevicostus. 



Spirifer marionensis Shumard. 



PI. IV. f. 12. 



Shell subsemicircular in outline, the width about one half 

 greater than the length, the extremities of the hinge-line 

 often extended into mucronate points, the two valves nearly 

 equally convex. Pedicle valve gibbous in the umbonal re- 

 gion, more or less compressed toward the cardinal extremi- 

 ties, the greatest convexity back of the middle; area narrow 

 with nearly parallel sides, extending to the hinge extremities ; 

 beak pointed and incurved; the sinus well defined, narrow and 

 angular at the beak but becoming broad and shallow towards 



• Geol. Iowa. V.pL VII. f. ,7. 



