PLATE IV li— Continueil 

 Tl!EMATlS OIll.AlA, Ulliill. 



Fif,'. 2(1. The hi-acliial vahc, i-i'taiiUTig- a jiortiiiii of the external oniainentation. X 2. 

 Kroiii a ■rntka-jiei-cha cast of the original six'cimen {itp. cit., tig-. Ifl). 

 Hiiilscm Rivei- j.'-i-oup. Cincinnati. Ohio. 



SCHIZOCRANIA, Hall imkI Whitkieli). 



P.ige m:. 

 ScHIZOCRANL\ (?) IfUDlS, Hull. 

 Fig-. 21. The exteiioi- of the brachial valve. X 2. 



Trenton limestone. Cliftmi, Teim. 



Schizocrania filosa. Hull. 



Fig-. 22. The extcrioi- of a brachial valve, attached to Strirphomena aUeniafn. X 2. 



Hudson River group. Cincinnati , Ohio. 

 Fig. 23. The exterior of a large brachial valve. 

 Fig. 24. The pedicle-valve. 



Utica .slate. Mohawk Valley, N. K 

 Fig. 25. A valve of tStrophomena alttrnata, to which five of these shell.« are attached, all of them exposing 

 the lower valve. 

 The figure is taken fi-oni the Pala;ontology of Ohio, vol. ii, pi. i. fig. 12, and the mu.scular scars on 

 the internal cast of the ui)i>er valve, shown in the left of the illustration, remain as there rep- 

 resented. 

 Fig. 26. An internal cast of the bi-achial valve ; showing the elongate, converging po.sterioi' scars, separated 

 into jiostei-ior and anterior elements; al.so a faint median ridge extending forward beyond the 

 muscular imj)i-essions. X 3. 

 Fig. 27. The jiedicle-valve seen on the right margin of fig. 2.5; showing the apical pedicle-callosity or 

 incipient groove. X 2. 

 Palfeontology of Ohio, vol. ii, pi. i, fig. 15. 

 Fig. 28. The pedicle-ai-ea viewed fi-om witliin ; showing more accni-ately the chai-acter of the apical cal- 

 losity, its median ridge and lateral walls indicating homology with the corresponding parts in 

 the genus Obbicl'loidea X 3. 



Huiison River grouii. Cincinuati, Ohio. 

 Fig. 29. An individual from which the ujiper portion of the brachial valve ha,s been remiive<l, expo.sing all 

 the internal characters of the pedicle-viilve. X 2. 

 it will be oKserved that in this figui-e, as well as in figs. 25, 33, 34 and 35, the diametei- of the 

 lower valve is less than that of the upper, and the former lies above and within the bas(^ of the 

 latter, the attachment of the .shell being- largely effected by the marginal portions of the larger 

 valve. 



Hudson Rivei- group. Covington. Ky. 

 Fig. 30. An internal cast of a brachial valve ; .showing the anterior and posterior muscnlai- scars. The 

 foi-mer impressions are rai-ely discei-nible. X 1.5. 

 Trenton limestone. Trenton Falls, N. Y. 



Schizocrania Schuchekti, sp. iiov. 



Fig. 31. A bi-achial valve, retaining a portion of the external ornamentation, but shuwing the posterioi- 

 mn.sinilar scars. X 3. 



Fig. 32. A smaller brachial valve, retaining most of the exterior surfac-e. X 3. 



Fig. 33. An individual from which most of the upper valve has been removed, exposing the pedicle-valve. 

 The features of the pedicle-area are not .so clearly retained iis to allow delineation. X 3. 

 Hudson River group. Covington, Ky. 



Schizocrania (?) Helderberoia, .si), nov. 



Fig. 34. The exterior surface of an individual ; showing the pedicle-valve, its coarsely radiate and obscure 

 concenti-ic striation, and the ovei-la|)|iiTig edges of the finely striated upper valve. The charactei' 

 of the pedicle-apertuie is not well retained. X 2. 



Fig. 35. The internal surface of the pedicle-valve ; showing what appears to be a broad pedicle-fisssure, 

 and the overlapping margins of the upper valve. X 3. 



Lower Heiderberg group. Nrar Clarksvillc, N. V. 



