482 PALAEONTOLOGY OF ILLINOIS. 



intermacular spaces. Here they are rather closely approxi- 

 mated, about six in two mm., with an average diameter of 

 0.18 mm. 



In sections the lunarium is illy defined, the zooecia appearing 

 as regularly oval or circular. The interspaces are occupied by 

 a single series of rather large, angular vesicles, but in the im- 

 mediate vicinity of the maculae they often form double series. 

 In vertical sections the zooecial tubes bend abruptly outward 

 from the irregularly flexuous median laminae, and, a short dis- 

 tance above the bend are usually crossed by a diaphragm. 

 The vesicles decrease in height toward the surface, and near it 

 are largely filled by a secondary deposit of sclerenchyma. 



The bifoliate zoarium suggests comparison with Meekopora, 

 Ulr., but I cannot find that the species approaches that genus 

 in any other respect. In its zooecial features it agrees closely 

 with the section of Fistulipora typified by F. communis Ulr. 



The specimen here figured is identical with a number of exam- 

 ples collected at Rominger's original locality by Mr. J. M. Nick- 

 les. It also agrees quite closely with an authentic example of 

 the species, the principal difference noted being a slightly greater 

 elevation of the lunarium in the latter. 



Position and locality: Hamilton group, near Alpena, Mich., 

 where it was collected by Rev. W. H. Barris, who kindly pre- 

 sented it to the author. 



MEEKOPORA Ulrich. 



(For generic diagnosis see page 383.) 



The two principal peculiarities of this genus, 7. e., the bifoli- 

 ate zoarium and the uniform direction of the zooecia apertures 

 toward the distal end of the zoarium, render it more than or- 

 dinarily easy of determination. In their general form and con- 

 struction the zoaria of Meekopora resemble those of Dichotrypa, 

 and the careless observer will probably confound them. A little 

 care, however, in comparing species of the t\vo genera will soon 

 bring to light several important differences, the genus under 

 consideration being an unequivocal member of the FISTULIPORIDJE, 

 while Dichotrypa is an equally true division of the CYSTODICTYO- 

 NID.E. A comparison of vertical sections brings to light some of 



