PLATE LII. 



Fenestella (L'nitrypa) lata. 



Page 136. 

 Fig. 1. An enlargement of a portion of the non-celluliferous face of a frond, showing- very regular 



branches and angular carinate dissepiments. (X 6.) 

 Fig. 2. An enlargement having a somewhat more i-obust appearance than the preceding. (X 6.) 

 Fig. 3. An enlargement ; the branche.s and di.ssei)iuient,s are partially imbedded in a sediment and jireaents 



a much more slender apjx'ai'ance than would be the case if the whole surfai* could be 



observed. Without a careful examination, this would seem to be the full size of the branches 



and dissepiments (X ti.) 

 Fig. 4. An enlargement, i-epi-esenting an impression in the rock ; the left of the illustration represents 



the impi-ession left by the carinje an<l cimnecling scalse, the right the impression of the cell 



bases. The tissue ha.s been pai-tially destroyed by maceration ; the solid portion left is the 



filling in of the cells and of the 8)Mu:e8 Vbetween the seals ; the solid oval spaces ai-e the tilling 



of the fenestrules. (X 6.) 

 Fig. 5. An enlargement of a portion of the celluliferous face of a ft-ond, showing the foi-m and ari-ange- 



nient of the cell apertui-es, the caiintR having \>een bi-oken away. (X 6.) 

 Fig. ti. An enlargement of the summits of the carina; ami the seals- connecting them. 

 Fig. 7. An enlargement ; the upper left comer repi-esent.s the non-celluliferous face of the branches ; the 



remainder of the illu.stration repi-esents the base.s of the carinjp, that is, the portion joining the 



celluliferous face of the branches and the under aide of the scalte connecting the carinte. The 



entii-e substance of the cell-bearing portion of the branch has been i-emoved from this portion 



of the specimen. (X ti.) ' ' 



Fig. 8. An enlargement ; the upper portion of tfie figui-e i-epresenting the intenor of the branches and 



the exterior with cell apertui-cs ; the lower anil left hand jwi-tion, the summits of the carina, 



and the scalie connecting the carina". (X •> ) 

 Fig. 9. A lateral view of a branch enlarge<l, showing a transverse section of tile rtissepiments. and the 



Rcalie connecting the carinK, which ai-e abruptly bent at a point a little above the middle of 



their depth. (X •).) 

 Fig. 10. A. fragment, natural size, comprising il jioflion of the base of a fronil. 



FeNESTET-F A (UnITKYPa) FICTICIITS. 

 Page up. 

 Fig. II. An enlargement ; the lower jwrtion represents the non-celluliferous face of the hi-anches ; the 

 ujijier portion the ba.Me of the carinie and the nmler 8i<le of the scaliP. (X H.) 

 An enlargement of a portion of the non-celluliferous face of a fronil. (X 0-) 

 An enlargement of the summits of the carina; and the obli<iue scaljE. (X tJ.) 



An enlargement of a jxirtion of the cellulifei-ous face of a fi-ond, having the carinse and scalte 

 removed, showing the form and aiTaiigement of the cell apertui-es. (X 6.) 

 Fig. 1.1. An enlargement of the luise of the carinae and the under side of the connecting scalse, .similar to 

 the upper portion of fig. 1 1. This illustration is given to .show how easily it might, by itself, be 

 mistaken for the (-ellulifi-rous face of .some form Of Fenestella. (X ti.) 

 Upper Helderlxirg giiiuji. IVnIjHile, Ontario, Canada. 



