CORALS AND BRYOZOA. 243 



tions proceed from the posterior part, and are elevated above the peristome, 

 obscuring the cell opening (pi. Ix, fig. 16). In the collections made from the 

 Hamilton group this is by far the most common species of Stictopora. 



This species most closely resembles S. Gilberti, of the Upper Helderberg group, 

 but the branches are usually narrower, the bifurcations less frequent, the mar- 

 gins straighter, much more gradually diverging, and are frequently notched 

 or serrated : from S. ovatipora it is distinguished by its usually wider 

 branches ; the less nearly parallel rows of apertures, and the margins of the 

 fronds are notched or serrated : from S. simosa, by the continuous longitudinal 

 ridges : from S. gronifera, by the continuous longitudinal ridges and absence of 

 granules on the ridges and peristomes : from S. palmipes, by the different man- 

 ner of growth, narrower and thicker non-cell uliferous margins, and the absence 

 of nodes or spinules on the longitudinal ridges. 



Formation and localities. Hamilton group, Lodi landing, Seneca county; North 

 Bristol, Ontario county ; near Geneseo, Livingston county ; Darien Centre, 

 Erie county ; Bellona, Yates county ; near Norton's landing, Cayuga county ; 

 near Canandaigua lake, Ontario county ; Borodino, Onondaga county, and other 

 localities in Central and Western New York. 



Stictopora trilineata, n. sp. 



PLATE LXI, FIGS. 26, 27. 



ZoARiDM consisting of a flattened, dichotomously branched frond arising from 

 a spreading base, or from several rootlets attached to foreign bodies ; for 2 

 or 3 mm. .above the base the stipe is cylindrical and has a diameter of about 

 1 mm., it then bifurcates and becomes flattened. Branches from 2 to 2.50 

 mm. in width, the margins essentially parallel, scarcely expanding before 

 bifurcating ; non-celluliferous marginal space very narrow, width less than .50 

 mm. ; transverse section of a branch lenticular, greatest thickness observed 

 .75 mm.; marginal angles acute; bifurcations frequently distant 10 or 12 

 mm.; branches usually diverging at an angle of about sixty degrees ; on some 

 of the fronds, near the base, there are occasionally lateral branches which 

 diverge at an angle of ninety degrees. Cells tubular, for a portion of their 

 length nearly parallel with the epitheca, then abruptly curving and opening 



