Bryozoa of the Hamilton Group. 67 



Dissepiments comparatively slender, less than .25 mm. in width, six 

 in the space of five millimetres; on non-poriferous side, on a plane 

 with the branches, rounded, carinated ; carina similar to the carina of 

 the branch. 



Fenestrules oval, length about .66 mm., width from one-half to two- 

 thirds the length. 



Cells in two ranges, opening nearly directly upward ; apertures 

 minute, circular, about .20 mm. in diameter, distance apart equal to 

 and slightly more than the diameter of an aperture, about twenty in 

 the space of five millimetres ; margins slightly elevated, and indenting 

 the border of the fenestrule ; space between the ranges of apertures 

 elevated, carinated ; carina thin, elevated, nearly equal to the thickness 

 of the branch, the upper half slightly expanded, and having a sharp, 

 thin crest, the carinas connected by their lateral projections or bars, 

 which are very thin and extend down the side of the carinae obliquely 

 about .20 mm., or a little more, about eighteen bars in the space of five 

 millimetres. 



Where the poriferous face is seen this species can be easily distin- 

 guished by the very thin lateral bars connecting the carinas, and their 

 comparatively great distance apart. The species of the genus Fenes- 

 tella are so similar in appearance, that without both poriferous and 

 non-poriferous faces, it is sometimes very difficult to assign a specimen 

 to the right species. 



Formation and localities. Ha'milton group ; Bellona, N. Y., and 

 West Williams, Ontario. 



^y Fenestella exornata, n. sp. 



Bryozoan probably infundibuliform, though occurring only in frag- 

 ments in the present collections ; largest fragment seen five centimetres 

 long and three wide. 



Branches moderately slender, appearing more slender on n on -porif- 

 erous side than on poriferous, gradually increasing in size to the bifur- 

 cations, which are distant from each other generally from five to seven 

 millimetres; branches from .33 to .50 mm. in width ; space between 

 the branches on non-poriferous side more than the width of branches, 

 on poriferous side about equal to the width, five or six branches in 

 the space of five millimetres ; on non-poriferons side flat, with a com- 

 paratively thin, sharp elevation around the edge of the fenestrules; 

 the space between these elevations flat or slightly concave, with fre- 

 quent, short, broad, conical spines, about .20 mm. in height. 



Dissepiments strong, frequently as wide as, or wider than the 

 branches, there are four in the space of five millimetres, greatly 

 expanding at their junction with the branches, on a plane, and having 

 the same appearance in every respect as the branches on their n on -porif- 

 erous side ; on poriferous side very much depressed and flattened. 



Fenestrules, on non-poriferous side, appearing broadly oval, on 

 poriferous side elongate-oval; length from three-fourths to one milli- 

 metre ; width on poriferous side .5 mm. 



