CORALS AND BRYOZOA. 207 



moderately thick, sub-equally elevated, and having on one side two denticula- 

 tions. Inter-apertural space flat, smooth or with indications of the vesicles 

 below. Surface marked by prominent, conical monticules, the centers of 

 which are distant about 7 mm., and have cell apertures larger than the 

 others, more oblique and pustuliform, often presenting a confused appear- 

 ance. When the frond is worn or macerated the surface presents a much 

 different aspect from that of well preserved specimens ; the cell apertures 

 are obscurely trilobate ; the peristomes are strong and equally elevated ; the 

 inter-apertural space is occupied by minute angular pits, the margins of 

 which are elevated a little less than the peristomes. 



In having conspicuous opercula this species resembles L. operculata and 

 Fistulipora serrulate ; from the former it may be distinguished by the more 

 prominent and more frequent monticules, the equally elevated peristomes, the 

 absence of bullae on the inter-apertural surface, and the prominent apertures at 

 the center of the monticules ; in that species there is a circular space destitute 

 of cell apertures : from F. serrulata it may be distinguished by the more promi- 

 nent monticules, more closely disposed cell apertures, the presence of denticula- 

 tions and the absence of mesopores ; in the pustuliform apertures at the center 

 of the monticules it resembles L. conulata of the Upper Helderberg group, but 

 the mode of growth is different, the monticules are much larger and more 

 distant, and the ordinary cell apertures are not pustuliform : from the other 

 species, at present known, it may be distinguished by its conspicuous opercula 

 and the prominent pustuliform cell apertures of the monticules. 



Formalion and locality. Hamilton group, York, Livingston county, N. Y. 



LiCHENALIA TESSELLATA, n. sp. 



>OT rlaUHBD. 



ZoARiuM consisting of flattened expansions or of masses formed by the accretion 

 of successive layers of growth; fronds observed from 2 to 5 mm. in thick- 

 ness; epitheca very thin and, on the specimens examined, not strongly 

 wrinkled concentrically, as in nearly all other species. Cells tubular, 

 apparently polygonal, generally rectangular to the surface, walls thin. 



