CORALS AND BRYOZOA. 183 



or less prominent ridges, which are sometimes straight, but usually sinuous 

 and occasionally irregular ; generally only one ridge between adjacent rows, 

 but rarely two ; when the apertures are irregularly disposed the ridges appear 

 interrupted and involved. Peristomes very slight, scarcely perceptible. 

 Between adjacent cell apertures there are usually two comparatively promi- 

 nent, hollow, conical nodes, which, in the course of growth, form minute 

 curved tubuli between the cells. One specimen shows indications of the 

 longitudinal structure characteristic of the genus Rhombopora. 



Some specimens of this species closely resemble forms of Acanthoclema 

 Hamiltonense, but the longitudinal ridges are less prominent and more irreg- 

 ular, and there are prominent nodes between the cell apertures in place 

 of pits, internally it is without the filiform axis characteristic of the genus 

 Acanthoclema. From A. altematum of the Upper Helderberg group it may 

 be distinguished by the less prominent and more irregular, longitudinal ridges, 

 and by the smaller size and greater number of nodes : from T. {().) irregularis 

 it is distinguished by its less prominent and more irregular longitudinal ridges 

 and the conspicuous nodes. Its general appearance is similar to T. (0.) cari- 

 nata, but there are more ranges of apertures on a branch, the longitudinal 

 ridges are not so rigid and prominent and are more irregular, and there are 

 usually two nodes between adjacent apertures, there being only one in that 

 species. 



Formation and locality. Hamilton group, Moscow, Livingston county, N. Y. 



Trematopora (Orthopora) elongata, n. sp. 



PLATE LV, FIG. II ; AUD PLATE LVI, FIG. 16. 



ZoARiUM ramose ; bifurcations infrequent, sometimes distant 30 mm. ; branches 

 frequently diverging at an angle of nearly or ([uite ninety degrees, diameter 

 about 1.25 mm. Cells tubular, arising from the centre of the branch, 

 about 1.50 mm. long, oblique, straight and in contact for the greater portion 

 of their length, abruptly bending outward near the surface, apparently 

 without septa. Cell apertures elongate-oval, length about .25 mm., width a 



