CORALS AND BRYOZOA. 187 



I have hesitated to place this species in the sub-genus Orthopora on account 

 of the irreguliir disposition of the cell apertures, but the internal structure, 

 except as noted in the last sentence, is precisely the same as in undoubted 

 species of that sub-genus. 



This species most nearly resembles T. (O.) transversa and T. (0.) elongata, but 

 it may be distinguished from both these by the irregular disposition of the 

 cell apertures ; from all other species of this geological formation it is dis- 

 tinguished by the numerous, comparatively prominent nodes on the elevated 

 surface between the cell apertures. 



Formation and locality. Hamilton group, Owasco Lake, N. Y. 



Trematopoea (Orthopora ?) transversa. 



PLATE LV, FIG. 12; AND PLATE LVI, FIGS 13, 14 



Trtmaiopora trannversa. Hall. Trana. Albany Institute, vol. x, p. 180. 1881. 

 " Report of State Geologist for 1883, p. 8. 1884. 



ZoARiUM ramose, bifurcations infrequent, branches widely diverging, diameter 

 about 1.75 mm. Cells tubular, arising from the centre of the branch, length 

 1.50 mm., for the greater portion of their length in contact, gently curving, 

 and abruptly turning outward near the surface ; septa near the center of the 

 branch wanting, in the outer portion numerous, thicker than the cell walls, 

 generally extending only partially across the cavity. Cell apertures oval, 

 length .22 mm., width generally about one-half the length, usually disposed 

 in longitudinal rows, frequently alternating and forming oblique transverse 

 rows, and sometimes irregularly disposed. Peristomes moderately strong, 

 slightly elevated. Surface between the cell apertures flat or slightly con- 

 cave, with numerous small nodes or granules, one or two series around each 

 aperture. The nodes in the course of growth form minute curved tubuli 

 between the cell apertures. 



This species most nearly resembles T. (0.) elongata, but may be distinguished 

 by the thicker branches and more broadly oval cell apertures. The cell tubes 

 are more regularly curved and the interstitial cells are more numerous, the 

 septa are stronger, occur much more frequently and extend only partially 



