GIRTY, NEW CARBONIFEROUS FOSSILS 195 



eter of the upper side is 28 mm. and the height 22 mm. (perhaps .30 mm., when 

 complete). It does not consist of superposed layers, but the cells are contin- 

 uous and consequently 20 mm. long or more. They are very irregular in size. 

 Some of the smaller ones are suggestive of mesopores, but may be merely 

 immature cells, the introduction of which was necessitated by the radiating 

 direction of the zooecial structure. There is no conspicuous arrangement into 

 maculie, the very largest and the very smallest being contiguous in many 

 cases. To a certain extent, however, the smaller cells are grouped together 

 (interspersed with others), but there are considerable spaces without them. 

 Even if the very small cells are avoided, the number varies considerably. 

 When a row of large ones is brought under the microscope, a little over 5 

 occur in 2 mm., while as many as 7 of the smaller or 6 to 6% of the medium 

 size occur in the same distance. The large cells vary from .28 to ..35 mm. in 

 diameter. 



The walls are somewhat thickened. In some instances, the median line can 

 be seen, but it is not conspicuous. The acauthopores are small and may be 

 readily overlooked. They do not indent the cells, being determined chiefly by 

 a densification of the material at the .iunction of the walls. In longitudinal 

 section, the characteristic annular thickenings are almost absent. The dia- 

 phragms are situated at irregular, usually long intervals, seldom as close to- 

 gether as the diameter of the cell — sometimes three or even four diameters 

 apart. The maximum interval observed is about 1..5 mm. The diaphragms 

 occur throughoiit the length of the tubes examined. Their charactei'istic 

 perforations are clearly shown in many instances. 



Stenopora emaciata var. inaequalis var. nov. 



Typical Stenopora lonpicnuicrata is based on a form which grows in hemi- 

 spherical masses and has long zooecial tubes intersected by relatively few 

 diaphragms. Ajiother and much more abundant type occurs in the collection 

 which resembles longicamerata in most of its microscopic characters, but dif- 

 fers in having an explanate mode of growth. The thin sheets, which seldom 

 have a thickness of more than 4 mm., are much contorted, in some cases bend- 

 ing around completely so that the edges are confluent and hollow cylinders 

 are formed. The cell walls are thin, with only occasionally a beadlike swell- 

 ing. Transverse sections show thick- as well as thin-walled areas, the thick- 

 ened walls being probably where the section passes through these swellings. 

 The acanthopores are small and the diaphragms relatively distant. 



Stenopora emaciata var. arkansana var. nov. 



Zoarium consisting of lamellar expansions covered on the under side by a 

 wrinkled epitheca. The expansions seem to range to 20 mm. in thickness, 

 but are usually less than 10 mm. and in many cases much less. Relatively 

 massive bodies are formed by the superposition of successive layers which are 

 irregular in thickness and in shape, being often much contorted. 



Zocecia rather large, very variable in size, aggregations of larger ones form- 

 ing maculre. The maximum diameter of very large cells is .7 mm., but as a 

 rule, the lar.ger ones are not over ..56 mm. in diameter and the smaller ..35 mm. 

 (even .29 mm. or less). Thus, al)out 4 of the larger ones or 5.5 to or 7 of 



