CORALS AND BRYOZOA. 275 



the primary rachis ; this mode of growth is continued indefinitely, the 

 fronds covering a comparatively large area. Cell tubes sub-cylindrical, 

 sinuous, especially near the base, the attached portion flat, the free portion 

 convex; length about 2 mm., width .50 mm., turning abruptly outward at 

 the extremities, the apertures being parallel with the axis of the branch 

 and broadly oval, generally alternating, occurring at intervals of about 

 1.33 mm.; for a short distance they are nearly parallel with the rachis, then 

 diverging at an angle of from thirty-five to forty degrees, margins of the 

 branches in contact, but not coalescing, the end of each succeeding cell 

 tube projecting beyond the previous one, giving a serrated appearance to 

 the margins of the frond. In well-preserved specimens the cell tubes are 

 strongly annulated and generally obscurely angular along the middle, giving 

 the annulations the appearance of a row of nodes ; on some portions of the 

 frond the cells are not angular, but the annulations still have somewhat 

 the appearance of nodes along the middle of the tube ; the annulations are 

 broad, abruptly rounded, three in the space of 1 mm., with indications of 

 faint longitudinal striations. 



This species forms comparatively large fronds, fragments occurring nearly 

 100 mm. in length ; numerous branches apparently originate at a common 

 ba.se ; on different fronds and on different portions of the same there 

 is a great irregularity in the frequency of branching ; on one specimen there 

 are five widely diverging branches in the space of 60 mm. ; on another 

 frond in the same space there are fourteen branches, diverging at an angle 

 of thirty degrees, on one portion three branches in the space of 7 mm. The 

 branch becomes gradually narrower toward the extremity, the last cell being 

 terminal and extending beyond all the others. All the specimens observed 

 occur upon the shells or casts of Cephalopoda. 



This species may be distinguished from R. nodata by the narrower cell tubes, 

 and the much less prominent annulations and nodes ; from Hederella conferta by 

 the difference in the character of the rachis, the more regular arrangement of 

 the cell tubes, and the prominent annulations. 



Formation and locality. Hamilton group, Cazenovia, Madison county, N. Y. 



