PLATK II— Contiiiueil. 



BARROISELLA., geii. uov. 



Page 62. 



Bakhoisella subspatulata, MecU ;uul WdiIIicii. 



Fi". H. The <-iU-ilinal portion of the pedicle-valve ; showing- the conspicuous pedicle-gi'oove, whicli, in this 

 " instimce, has been somewhat widened by compression and fracture ; also the articular Ixisses 



or <;ar<linal fulcra on the basal margin. X 5. 

 Fig. 15. The interior of a pedicle-valve ; showing the cardinal area, nuiscular and other markings. X 3. 

 Fig. 16. The inteiior of a brachial valve, with characteristic features. X 3. 



Ulack slate (Genesee slale). IVhife mivi; near Ruckford. Tndinna. 



LINGULASMA, Ulkicii. 



Page 24. 



Linoulasma Schuoherti, Ulricli. 



Fi"-. 17. The apical p<ii-tion of the internal cast represented in tig. 22 ; enlarged to show the impression of 

 the pedicle-sheath (ps), or internal continuation of the cardinal area. X 3. 



Fig. 18. The interior of a brachial valve ; showing the character of the musculai- imjii-essions, the platform 

 and the very strong septum. Di-awn from a gutta-percha impression of an internal cast. 

 Natural size. 



Fig. 19. Profile view of an internal cast ; showing the relative thickness of tlie platforms on the two valves. 



Fig. 20. The intei'ior of the pedicle-valve ; showing the pedicle-slieath (ps), the indislinctly detineil muscu- 

 lar impressions, the low platform and inconspicuous septuTU. This drawing is also made from 

 a gutta-percha impression. Natural size. 



Fi". 21. An enlargement of th(' surface ornamentation. The tubercles are sharply defined, and round on 

 the median jiortions of the shell, but become elongated and less distini.'t toward the lateral mar- 

 gins. X 5. 



Fig. 22. A natural cast ; showing the intei-ior of the brachial valve. 



Fi"-. 23. The opposite side of the same specimen; showing the intei-iiMl char.acters of the pedicle-valve. 

 Hudson River group. Wilmington, lUinoiH. 



LfNGULOPS, Hall. 



Page 18. 



LiNGrLOPS NoRWOODi, James. 



Fig. 24. The exterior of a pedicle-valve. X 4. 



Fi". 2.5. The interioi' of a pedicle-valve, drawn from a gutta-percha imin-ession of a natural cast. The 



pedicle-groove is faint but evident : within the broad po.sterior margin lie the compound um- 



bonal or cardinal impressions ; the scalloped posterior and the median muscular scars are very 



sharply defined. X 8. 

 Fig. 2H. The interior of a brachial valve ; showing the low, elongate platform. The punctEe on the .surface 



of the platform ajipear to be regularly arrangeil liiit are jirobably accidental markings. 



Drawn from a gutta-percha impression. X 6. 



Hudson River group. Vincimiati, Ohio. 



LiNuuLOPs Whitfieldi, Hall. 



Fig. 27. The extei-ior of a peiiicle-valve. X 0. 



Fig. 28. The interioi- of a jiedic^le-valve ; the original sjiecimen. The figure has been drawn from a gutta- 

 percha impres-sion of an internal cast, and shows the comjmund cardinal ai-ea (seen also in fig. 

 30), the \\\m:v portion of which is concentrically striated ; the crescent (rr) ; the scalloped pari- 

 etal scar and mi'dian muscular scars ; the narrow longitudinal septum Hanked by broad, ronndeil 

 ridges continued from the visceral region. No traces of vascular impressions are visilile on 

 the specimen. X 12. 



Fig. 29. An imperfect interior, i>n)h!it)ly belonging to the same (pedicle-) valve. X 12. 



Fig. 30. The interi(n- of the brac-hial valve, drawn from a gutta-pei-cha impression ; showing the double 

 car<linal area, a faint pedicle-deiiressinn, the crescent (cr), the ]iaric!tal (0 scars, the platform, 

 and the va.scular .sinuses with their outer ramifications. X 10. 



HiKlson River group. Maquoketa Creek, 12 miles north-wst of Didmque., lawn. 



