140 THE PALEONTOLOGY OF MINNESOTA 



[Euridictya. 



rows between longitudinal plates. The end or transverse partitions appear less sharp 

 than the longitudinal lines, are generally a little curved, and cross the spaces at either 

 a right angle to the direction of the growth, or somewhat obliquely. In the latter 

 case the primitive cell is subrhomboidal in shape. In the succeeding stage we see 

 the structure immediately following the formation of the original aperture, i. e., the 

 beginning or lower part of the vestibular portion of the zoarium. Now the zocecial 

 cavity is rounded, of elliptical shape, with a thin ring-like wall, generally in contact 

 with the longitudinal plates. The latter appear usually as dark structureless lines 

 separating the rows of cells. The end spaces, in part at least, may be empty (i. e., 

 filled with clear calcite) thus indicating the presence of interstitial vesicles. In 

 the third or superficial stage, the interstitial vesicles have been filled with solid tissue 

 and the diameter of the zooecial cavities generally reduced a little by a thin internal 

 deposit, while the dark longitudinal lines are now clearly resolvable each into a 

 crowded row of exceedingly minute tubuli. 



Some of the St. Paul specimens look very much like wide examples of the large 

 variety of Ehinidictya mutaUlis, but after one becomes familiar with the peculiarities 

 of each, it is not difficult to distinguish them. In the first place the zoaria of the var. 

 major have always an aged appearance, being heavy, with subparallel, rounded edges, 

 thick interspaces, and correspondingly narrow zooecial apertures. The small speci- 

 mens of E. multipora, on the contrary, are thin, sharp-edged, oftener and more irreg- 

 ularly divided, and with comparatively thin interspaces. When we compare thin 

 sections the differences are as shown on plate VI, by figs. 1 and 9, 6 and 10, and 11 

 and 12. 



Both E. calhounensis Ulrich, and E. montifem Ulrich, have a well developed 

 superior hemiseptum, but no interstitial vesicles. In other respects the first is 

 rather closely simulated by the present species. There is no associated species with 

 which E. multipora is likely to be confounded. The Ehinidictya var. major is not 

 found, as far as known, so high in the shales, being restricted apparently, like Phyl- 

 lodidya varia, another wide bifoliate form, to the middle division of the Trenton 

 shales. 



This species, as above cited, was described by me from Kentucky specimens. 

 Since then 1 have found it in Tennessee, and in 1885 a single example in the Minne- 

 sota State collection proved to belong to the same species. Two years later Mr. 

 Schuchert and the writer secured about ten specimens at St. Paul.* Respecting the 

 specific identity of all these specimens with the originals of Hall's Phcenopora multi- 

 pora, I should say, that I am still of the opinion expressed in 1882, but having since 



* During the past two weeks (to April 10th, 1802,) tlio writer secured no less than -fifty specimens at St. Paul.' 



