PLATE XlB— Continuetl. 



Steeptorhynghus Ulrichi, sp. IIOV. 



Fig. 15. The interior of ;i pedicle-valve, referred to the genus on acconnt of the peculiar form of the shell 

 and the absence of median septum or dental plates. 



Chester limestone. Cnttenden county, Kentucky. 



Genus DEEBYA, Waagen. 



Page 261. 

 DEEBtA (?) COSTATULA, Sp. IIOV. 



Fig-. 16. View from the brachial valve of a small specimen, which shows the characteristic surface orna- 

 mentation of this species. This consists of strong radial ]-ibs alternating with fascicles of two, 

 three or four liner striae. X 2. 



Fig. 17. The cardinal jn'ocess of a brachial valve similar in external characters to that of the preceding 

 specimen. X 3. 



Chester limestone. Crittenden county, Kentucky. 



Genus MEEKELLA, White and St. John. 



Page 261. 

 (See Plate X, figs. 18-23.J 



Meekella occioentalis, Newberry. 



Fig. 18. View of the brachial valve of an internal cast which retains a portion of the shell over me cai-dinal 

 area of the pedicle-valve. The deltidium of this area shows the same structure as in the fol- 

 lowing species and in the genus TRrrLECiA, a considerable portion of the coverving between the 

 dental ridges being flat or slightly concave, the convex ridge being confined to the middle of 

 the plate. The apex of the brachi.il valve is removed, showing (imperfectly in the figure) the 

 basal poi'tion of the inner surface of the cai'dinal process. 



Fig. 19. An incomplete intei-nal cast of the pedicle-valve ; showing the extension and convergence of the 

 dental lamells and the fine radial lines upon the surface of the plications. 

 Both figures are from the original specimen of OrtJiisina occidentalis, Newberry. 

 Upper Carboniferous limestone. Canon of Diamond River. 



Meekella striatocostata, Cox. 



(See Plate X, figs. 18-23.) 

 Fig. 20. Cardinal view of a large, symmetrical individual, essentially an internal cast in chei't ; showng 

 the position of the dental and crural plates. 



Upper Coal Measures. Winterset, Iowa. 

 Fig. 21. Cardinal view of a distorted specimen, with an unusually high cardinal area. 

 Fig. 22. The form of the cardinal process, from a gutta-percha impression of a natural mould. X 3. 

 Upper Coal Measui-es. Lawrence county, Kansas. 



Genus DERBYA, Waagen. 



Page 261. 

 (See Plates X, XI and XIa.) 

 Derbya crassa, Meek and Haydeii (?). 

 (See Plate X, figs. 10, 11 ; and Plate XIa, figs. 28-33.) 

 Fig. 23. A ijortion of the internal surface of the brachial valve of Productus Nebrascensis, to which are 

 attached several minute pedicle-valves, some of which show the i^resence of a broad cardinal 

 area, deltidium and a median septum. It will be observed that most of the attached shells 

 have their hinge-lines pai-allel to that of the Productds, though their relative positions are in- 

 verted. X 3. 

 Fig. 24. A further enlargement of three of these shells ; showing all the details of structure that are i-e- 

 tained. These attached valves seem to be the young of some streptorhynchoid species having 

 a median septum in the pedicle-valve, and as Derbya cra.ssa is the most abundant of these forms 

 in the associated fauna, the fossils may be tentatively referred to this species. X 10. 

 Upper Coal Measures. Near Kansas City, Missouri. 



