PLATE II— Continued. 



OBOLELLA, Billings. 



Page (iii. 



Obolella crassa, Hall. 



Fig-. 31. The exterior (li !i valve. Natural size. 



Fi"- 32. The same, enlarged ; j-howin- the radiati,,- st,-ia; between the lamellose -i-o«th-ln,es. X -. _ 



■ Fig. 33. Another valve, similarly enlar-e.l, in whi.-h the radiali,;^' lines do not appear Tins ,s the speci- 

 men ori-inally descril)ed as Avicuhi dcsqaamata. Hall (Pal. N. > ., vol. i. 1M7). 



Fig-. 34. The interior of a pedicle-valve ; shonin- the pediele-g-roove, the car.linal. lateral and (-ent,-al mus- . 

 cular scars. X 2. 



Fi"- 35 The interior of another, but .smaller, pedicle-valve ; showing: the same teatures. X -. 



Fig. 36. The interior of the brachi.al valve; shoNvin.-thefai.it pedicle-g-roove, the caninial, exte,-na,l, cen- 

 tral and 1,-itei-al muscular impressions. X ii- 



Middle Cambrian. Near Troy. N. T. 



Obolella polita, Hull. 



Fig. 37. The exterior of a valve, X 4. ■■ ^ , 



Fig. 38. The interior of a pedicle-valve ; .sliowing the central and lateral n.usrnlar nnpressions. X - 

 Fig. 39. An internal cast of the opposite (!) valve. X 2. 

 Fig. 40. The interior of a brachial v.alve X 6. 



Fig. 41. The interior of a pedicle-valve. X li- , „ . ^r v ^. . 



(Figs 40 and 41 are from the origi.,.-d drawings represents m the Sixteenth Kept. N. V. State 

 Cab, Nat. Hi.st.. pi. vi. tigs, 20, 21.) 



Potsdam sandstone, Trtmpahaii, Wisconsin. 



Or.OLELLA GEMMA, Billillg.S. 



Fig. 42. The exterior of a pedicle-valve. X tj. . 



Fig. 43. (34 in error, last line of figures.) The interior of a brachial valve ; showing the muscular un- 



pressions. X 6. ,. , • j i • 



Fig. 44. The interior of a pedicle-valve ; showing the ,-ai-dinal area, pedicle-groove and muscular un- 



(Tte orS^s ^ lis. 1. 2, 4, 34, 35. 30. 42. 43, 44, are in the collection of Mr. S. W. Foko.) 



