PLATE IVg. 



Legend. 15. ]3rii(rliial valve. o. Central scars. 



P. Pedicie-valve. [ic. Posterior centrals. 



F. Foramen. cc. Median centi-jiis. 



p. Pedicle-callosity (in brachial valve). ac. Anterior centials. 



g. Pedicle-g-roove. jia. Posterior addiuitors. 



g'. Base of groove. jia'. Anterior element of posterior ad- 



1. Walls of groove. ductoi'S. 



f . Meilian .septnni. aa. Anterior adiliictor.s. 



o. Posterior musculiir si'ar.<. 



T1;I:MATI8, Sii.vun:. 



I'age 13S 

 TkEMATIS TEKMINALIS, EllimoilS. 



Fig. 1. The interior of a brachial valve; .showing the postei-ior and central mnscnlar .-Jcai-s and the lingui- 



form median elevation. X 3. 

 Fig. 2. An internal cast of the pedicle-valve : showing the great depression of the jiedicle-area, the 



median ridge corresponding to the pedicle-groove, and the vascular sinnses. X 3. 

 Trenton limestone. Mkldleritli', JV. Y. 



Tke-Matis, sp., ionii)aie T. punctostkiata, Hull. 



Fig. 3. The internal pedicle-area ; showing the elevation of the mai-gins of the tissnre. X 4. 

 Huilson River group. Frankfort, Ky. 



TllEMATIS MILLIPUNCTATA, Hall. 



Fig. -1. The inteiior of a brachial valve : showing the posterioi' callosity forming a surface iov the pa.s.sage 

 of the pedi(-le, the external muscular scars and the components of the centra! imjiressions. X 2. 

 Hudson River gi-oup. Covington, Ky. 

 Fig. • 5. An intei'nal cast of a brachial valve, to which a portion of the shell adhei-es. X 2. 

 Fig. 6. The exterior of a brachial valve, from which the shell is partially exfoliated, X 2. 

 Fig. 7. Pi'ofile of an internal cast of the conjoined valves. 



Fig. S. Anteiior view of the same specimen, exposing the pedicle-valve and the iirojectitig apical portion 

 of the brachial valve. X 2. 



Hudson River gi-oup. Cineinnnti, Ohio. 

 Fig. 0. The interior of a brachial valve ; showing the jiosterior uiiiscular scars beneath the broken pedi- 

 cle-callosity. X 15. 



Hudson Ri\-er group. Frankfort, Ky. 

 Fig. 10. The external ornamentation. X 25. 



Trematis punctostkiata, Hall. 

 Fig. 11. The exterior of a brachial valve. X 2. 

 Fig. 12. The intei-ior of a pedicle-valve. X 2. 

 Fig. 13. The external ornamentation. X 25. 



Trenton limestone. Clifton, Tenii. 



Trematis fragilis, Uliich. 



Fig. 14. A peilicle-valve ; showing the short and nari'ow pedicie-tissnre. 

 Hudson River group. Bank Lick Creek, Ky. 



Trematis Ottawensis,' BilUiig.s. 



Fig. 35. External view of a brachial valve. From a gutta-percha cast of the exterior. Natural size. 

 Pig. IB. The surface ornamentation. X 25. 



Trenton horizon. Frankfort, Ky. 

 Fig. 17. The external pedicle-area, from a specimen )-eferred with dmibl to this specie.s. X 3. 



Hudson River gron]i. Cincinnati, Ohio. 



Trematis u.mboxata, I'hicli. 



Fig. 18. The exteiior of the brachial valve. X 2. 



Fig. 19. The same specimen, with the upper portion of the brachial valve removed, exjiosing the flat lower 



valve and its peiiicle-tissure. X 2. 

 From the original .specimen tigui'ed by Ulhich (American Geologist, vol iii. No. 6, p. 378, fig. 8. 



1889). Hudson River group. Covinr/ton. Ky. 



