Paleoutology of the Ciiiriiinafi Croup. 155 



Surface witliout distinct organic markings. Branches ar- 

 ranged in the proportion of from 25 to 28 in the space of an 

 inch." (Canadian Organic Remains, Decade II, 1865, p. 136). 



Sub-class (jKAI'Tolitoidica. 



Hydrozoa, in which tlic hydrosoma is compound and free, 

 consisting of numerous polypites united by a coenosarc, the 

 latter being enclosed in a strong tubular polj'parj^ while the 

 former are protected by hydrothecce. The polypites not sep- 

 arated from the coenosarc by any partition, and the polypary 

 generally supported by a chitinous rod or solid axis. (Nichol- 

 son, Monograph Brit. Grapto., 1872, p. 99. See also for a full 

 explanation of the features of various members of the sub- 

 order, Manual of Paleontolog}^ Nicholson, vol. i, 1889, pp. 

 210-222). 



Remarks. — In this sub-class are included the majority of the 

 Graptolites. The limited number of species known from 

 Cincinnati scarcely justifies an elaborate classification, but 

 the key presented below is perhaps as natural a one as can be 

 given with our present knowledge of the more obscure forms. 



Key to Genera. 



a. MoNOPRiONiD.^v — /. e., polypary with cells on one side 

 only. 



1. Graptolithus — Polypary simple and unbranched. 



b. DiPRioxiD.!-;— /. e., polypary with cells on both sides. 



2. Diplograptus — Cell mouths at the end of projecting 

 denticles. 



3. Climacograptus — Cell mouths apparently sunk beneath 

 the substance of the stipe. 



4. Dicranograptus — Cell mouths as in No. 3 ; the main stem 

 with cells on both sides ; the branches with cells on one 

 side onh'. 



c. MuLTiPRiONiD.K — J. e., with many cells, without definite 

 arrangement. 



5. Megalograptus — Cell scattered over polypary, but not on 

 margin. 



d. Insert.E Sedis — i. e., of uncertain position. 



6. Inocaulis — Cells unknown ; branched and rough, gen- 

 erally in groups. 



7. Dawsonia — Polypary unknown ; ovoid bodies supposed 

 to be ovarian capsules. 



