PI^ATK IVh— Comiiiue.!. 



Crania sictifera, H;ill. 

 Pig-. 18. A somewhat impei-fect U))i)er valvo. 



Niagara group. Walrlron, Indiana. 



Crania oranosa, s|i. nov. 



Fig. 19. A soiiiewliiit (iistorted uppei' valve ; showing tlieliiiely granulose surface. 

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



Hamilton group. CeiUerJield, N. ¥■ 



CiiANiA Trentonensis. Hall. 



Figs. 21, 22. Ki'ont and profile views of an upper valve. 



Trenton limestone. Middleville, N. Y. 



Crania scariosa, Hall. 



Fig. 23. A brachial valve of Strophumeiia alteriiala, covei-e<l with shells of this species all of which carry 

 the radiating and fine concentric ornamentation of the host. 



Fig. 24. The interior of an upper valve, the extei-nal sui'face of which is overgrown by a Monticulipora. 

 The jiosterior adductors are larger than the anterior pair, and near their outer edges the small 

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

 pressions appear as dark discolorations of the shell, indicatitig a probable greatei' density of 

 the shell-snbstance. X 2. 



Fig. 2."). The interior of a lower valve. The posterior scars are more distant ami smaller than in the 

 opposite valve, while the anterior scars are much largei-. X 2. 



Fig. 20. A shell of Platysirophia lynx, having the surface of the brachial valve crowded with indiviiluals 

 of this species. 



Hudson River group. Cincinnati, Ohio. 



Crania multipunci'ata, Miller (= Cnniiit sca/iiosa, Hall). 



Fig. 27. One of a gioup of in<liviiluals attached to a fragment of Monticilipora. The punctate surface 

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

 of Tremalia tri'ininxili.'i. X 2. 



Hudson River group. Covingtun, Ky. 

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

 Hudson River group. Blanchester, Ohio. 



Crania socialis, Uliich {== Crania .•imbin.tn , Hall). 



Fig. 29. A fragment of a ci'inoid colunm, covered with individuals which retain very distinctly the impres- 

 sions of the sutui'es between the segments. X 3. 

 Hudson River group. Covington, Ky. 



Crania percarinata, Uhiih (= Crania .scahio-sa. Hall). 



Fig. 30. An individual which has been attached to some species of Pleukotomarh. X •?■ 

 Fig. 31. Another sjiecimen, which aUso l)ears the sui'face markings of some gastropod. X 3. 

 Hudson River group. Coinngion, Ky. 

 These figui'os are from Mr. Ulrich's tyjiieal sjiecimens. 



Crania, sp. iinv. ? 



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

 Lowei- Helderberg gi-oup. Near Clark.n'ille, N, Y. 



Crania favincola, sp. nov. 



Fig. 33. A lower valve, slightly broken about the posterior margin, but showing the very large posterior 

 muscular impressions, the deeply impressed anteriors, with sharply elevated margins and 

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

 Ffivogites pirnm, Davis. 



Hamilton gi-oup. Crab Orchard, Ky. 



Crania Leoni, Hall. 



Fig. 34. The interior of an upper valve ; showing, in addition to the posterior and anterior adductor scars, 



the faint impressions of the brachial muscles 

 Fig. 36. The exterior of an upper valve. 



Chemung giuup. Leon. N. Y. 



