PLATE XV. 



Fig. 



21. heda. Yinti, Kin^. Right valve, natural size ; testiferous. Byers's Quarry, 



22. — — Cast of a right valve (twice the natural size), showing 



muscular impressions. Byers's Q.uarry. 



23. Schizodus obscurus, /. Sowerhy. Left aspect; cast (natural size) showing im- 



pressions of the anterior and posterior adductor 

 muscles {a, b) ; pallial muscles {c) ; and visceral muscles 

 (d, e). Garforth duarry. 



24. — — Right aspect (natural size) of a cast. Garforth Quarry. 



25. Schizodus truncatus. King. Right aspect (natural size) of a testiferous specimen. 



Tunstall Hill. 



26. — — Umbonal aspect of the same. 



27. — — Right valve (natural size) of a testiferous specimen. Tun- 



stall Hill. 



28. — — Right valve (a little enlarged) of a testiferous specimen, 



showing marks of colour. Tunstall Hill. 



29. — — Representation of the dental system : 



A, Left valve. 



B, Right valve. 



a, Tooth fitting into pit, a* 

 h, Pit for tooth, b* 



c, Cleft tooth fitting into the triangular space, c* 



d, Pit for tooth, d*- 



e, Tooth for pit, e* 



f, Cartilage fulcra. 



(The numeral belonging to this figure has been inadvertently omitted. 

 The' letter B for the left valve, has been by mistake placed opposite 

 to the specimen at figure 31). 



30. Schizodus rotundatus, Brown. Cast, twice the natural size. Red Marls of Newton, 



near Manchester. Mr. E. W. Binney's specimen. 



(The figure makes the specimen appear more perfect than it 

 really is.) 



31. Schizodus Schlotheimi, Geinitz. Cast (natural size) of right valve. Marsden. 



32 f — — Left aspect (natural size) of a cast, with portions of the 



shell remaining on the lower half. Mr. E. W. Binney's 

 specimen. 



