PI^ATK IVh— CohUiiucm!, 



Crania setifeka, Hall. 



Fig-. 18. A somewhat imperfect upper valve. 



' Niag-ai-a gi-oup. Waldron, Indiana. 



Crania granosa, sp. iiov. 



Fig. 19. A somewhat distorted upper valve ; showing the Hiiely graiiulose surface. 

 Fig. 20. A portion of the surface enlarged. X 20. 



Hamilton group. Cenlerfidd, N. Y. 



Crania Tkkntonensis. Hall. 



Figs. 21, 22. Front and profile views of an upper valve. 



Trenton limestone. MiddlevUle, ]V. Y. 



Crania scario.sa, Hall. 



Fig. 23. A brachial valve of Strophoiiiciia alteriiaLa, covei-ed with shells of this species all of which carry 

 the radiating and fine concenti'ic oi'nanientation of tlie host. 



Fig. 24. The intei'ioi' of an upper valve, the external sui'face of which is ovei'grown by a Monticulipora. 

 The posterior adductors are larger tlian tlie anterior pair, and near their outer edges the small 

 scars of the adjnstors are discernible. In this species as usually preserved the muscular im- 

 pressions appear as <lark discolorations of the shell, indicating a probable greater density of 

 the shell-substance. X 2. 



Fig. 2.5. The interior of a. lower valve. The posterior scars are more distant and smaller than in the 

 opposite valve, while the antei'ior scars are much largei-. X 2. 



Fig. 26. A shell of Platyslrophia lynx, having the surface of the lirachial valve crowded with individcuils 

 of this species. 



Hudson River group. Cliidniiali., Ohii>. 



Crania multipunct.vta. Miller (= Crania srahiona, Hull). 



Fig. 27. One of a group of individuals attached to a fragment of Moxticumpora. The punctate surface 

 character of the host is impressed upon the shell, giving it a remote resemblance to the surface 

 of Tremails terminalis. X '.2. 



Hudson River grouji. Covinc/ton, Ky. 

 Fig. 28. Another specimen with similar surface markings. X 2. 

 Hudson River group. Blanchester, Ohio. 



Crania socialis, Ulrich (= Crunia scabwsa, Hall). 



Fig. 29. A fi-agment of a ci-inoiil colunm, covered with individuals which retain very distinctly the impi'es- 

 sions of the sutures between the segments. X 3. 

 Hudson River group. Covington, Ky. 



Crania percarinata, Ulrich (= Omnia scabiosa, Hall). 



Fig. 30. An individual which has been attiiched to some species of Pleueotomaria. X 3. 

 Fig. 31. Another specimen, which also bears the surface markings of some gastropod. X 3. 

 Hudson River group. Covinyton, Ky. 

 These figures are from Mr. Ulkich's typical specimens. 



Crania, sp. iiov. ? 



Fig. 32. The interior of an upper vahe of a probably smooth species. X 2.. 

 Lower Helderbei-g group. Near Clarksville, N. Y. 



■"; Crania fayincola, sp. nov. 



Fig. 33. A lower valve, slightly broken about the poslei'ior mai-giu, but showing the very large posterioi- 

 muscular impressions, the deeply impi-essed anterioi's, with sharply elevated mai'gins and 

 median fulcrum ; also, the radiating pallial sinuses. The shell is attached to a specimen of 

 Favosites pirum, Davis. 



Hamilton group. Crab Orchard, Ky. 



Crania Leoni, Hall. 



Fig. 34. The interior of an uppei' valve ; showing, in addition to the posterior ami anterior adductor scars, 



the faint impressions of the bi'achial muscles 

 Fig. 35. The exterior of an upper valve. 



Leon, N. Y. 



