PLATE IV B. 



Legend. a. Deltiilium. k. Platform-vaults. 



b. Deltulial slope. in. Median scars. 



c. Deltidial ridges. • n. Anteiior scars, 

 ca. Cardinal area. o. Lateral scars. 



ci'. Crescent. q. Ci'owu of crescent. 



d. Areal borders. r. Side of crescent. 

 h. Cardinal buttress. t. Transeverse scars, 

 i. Umbonal chanil)ers. u. Pallial sinuses. 



j. Platform. x. Umbo-lateral scars. 



TRlMEKELJvA, BiLi,ix(i,s. 



Page 33. 



TrIMERELLA LlXDSTRCEJlI, Dull. 



Fig. 1. The interioi- of an imperfect pedicle-valve; sliovving- the deep exca\ation at the base of the del- 

 tidiuni in the place usually occupied by the cardinal buttress. 

 Aymestry limestone. Island of Gotland. 



Trimekella gkandis. liillinojs. 



Fig. 2. An internal cast of a portion of a small pedicle-valve. 

 Fig. 3. The opjiosite side of the same. 



Guelph limestone. 6falt, Ontario. 

 Figs. 4, 5. Transverse sections, showing the structure of the platlbi'ni. 



TkIMERELLA ACUMINATA. RillillUS. 



Fig. 6. The interior of a pedicle-valve, .'somewhat restoi-ed about the umbo ; showing the platform, lateral 

 scars of the crescent and the ('xcjivate cardinal buttress. From a gutta-pei'cha impi-ession of 

 a natural cast. 



Niagara limestone. Port Byron, Illinois. 



HIIINOBOLUS, H.ALL. 



Page 44. 



KiiiNDBoLis Gai,ten.-<i.s, Billii)g.s. 



Fig. 7. The interior of a pedicle-valve; showing the narrow deltidiimi, Ijroad deUidiai ridges and the 

 small, imiierfectly developed platform. The drawing is made from a gutta-percha impression 

 of a mould of the interioi-. the specimen being that originally taken as the type of the genus. 

 Guelph limestone. Cfalt, Ontario. 

 Fig. 8. The interior of a small brachial valve. 



Guelph limestone. Ekyra, Ontario. 

 Fig. 9. The interior of a larger brachial valve ; drawn from the specimen figured by Wuiteaves on plate 

 8, fig. 3, Palseozoic Fossils, vol. iii, pt. 1. 



Guelph limestone. Hespeler or Durkajn, Ontario. 



Rhinobolus Davidsoni, S,i. IIOV. 



Fig. 10. a small pedicle-\alve, showing the internal characters. From a gutta-percha impression of a 



natural cast. 

 Fig. 11. The interior of a brachial valve, believed to belong to the same species. 

 Fig. 12. The interior of a larger brachial valve ; showing the undeveloped platform, the crescent and the 



transverse muscular scars. 



Niagara limestone. Gf-rafton, Wisconsin. 



