GIRTY, NEW CARBONIFEROUS FOSSILS 305 



have the mode of growth, bifoliate in the present type and ramose in 

 Idioclema, the entire absence of any structures resembling the hemisepta 

 seen in the latter, and the presence of a stage with numerous angular 

 mesopores and normal aeanthopores which is not found in Idioclema. 



On the whole, and chiefly because of the stage with distinct angular 

 mesopores and normal aeanthopores, I am including this form as a sub- 

 genus under Lioclema in which a group of species is also known having 

 a superficial sclerenchymatose deposit. In some respects, this form sug- 

 gests Intmpora (cf. I. hasalis) and some analogies can be drawn, but the 

 absence of hemisepta in the present form and of aeanthopores in Intm- 

 pora seems to show widely different affinities. 



Stenocladia frondosa sp. nov. 



Zoarium In the form of rather extensive though thin bifoliate fronds which 

 are considerably flexed or distorted and which divide and perhaps anastomose, 

 being considerably thickened at such points. Normal thickness .5 mm. to 

 2 mm. 



Zooecia small, longitudinal and thin-walled in the median portion of the 

 frond, considerably expanded toward the surface, near which they are directed 

 outward and have thick walls. The apertures are rounded and generally 

 somewhat elongated, .17 to .2 mm. in longest diameter. Eight or 9 apertures 

 occur in 2 mm. and they are separated by about one half their own diameter. 

 Cortical and mesial zones sharply and strongly marked. The cells are oblique 

 and the walls thin in the mesial portion ; the cells perpendicular to the surface 

 and the walls thick in the cortical portion, the changes being effected very 

 abruptly. The mature zone is of varying length in different specimens, rela- 

 tively narrower in the narrower specimens, ranging from about one third to 

 one sixth of the width on each side. Aeanthopores and mesopores are present 

 in abundance, but they are obscured near the surface by a deposit of scleren- 

 chyma, so that sections present remarkably different aspects, according as 

 they pass through different levels. Apparently in the young part of the ma- 

 ture zone, the mesopores are numerous and rather large, very variable in 

 numbers in different areas of the zoarium. They form rather extensive aggre- 

 gations or maculfe in some areas. In others the zooecia are in contact, with 

 the meso] lores distributed in groups of two or three, while in still others the 

 zooecia are separated by single rows of mesopores. Aeanthopores are fairly 

 numerous and small, but nevertheless they indent the cells more or less by 

 reason of the extreme thinness of the walls. Diaphragms are very rare and 

 appear to be non-perforated. They are confined to the zooecia. At the sur- 

 face, the mesopores are closed by a deposit of sclerenchyma, and the aeantho- 

 pores also seem to be modified to some extent. The surface namely appears 

 to be without spines and often without mesopores. though, when slightly 

 weathered, and perhaps here and there when not. the mesopores are clearly to 

 be seen in varying numbers as described above. When the mesopores are not 

 visible, the interspaces between the zooecia appear to be thick and structure- 

 less. Thin sections just at the surface show few. if any. mesopores. Acan- 

 thopore'^ are mmiornns. Wlioreas below the snrfaoe thoy appear as small 



