448 PALAEONTOLOGY OF ILLINOIS. 



and ramulosa, belong to the St. Louis group. They are remark- 

 ably alike in tangential sections, but the first grows in irregu- 

 lar hollow branches, while the second forms small solid ramulets. 

 Two species differing from each other in precisely the same 

 manner, and from the St. Louis forms, by their much thicker 

 walls and somewhat smaller cells, occur in the Chester group. 

 The one I have called A. solida, the other must await an op- 

 portunity for publication. The sixth species is A. symmetries, 

 the type of the genus. It is not uncommon at several Chester 

 localities in Kentucky, and I have also seen specimens from Illi- 

 nois, that were collected by Mr. J. M. Nickles at Chester. A 

 good example is figured on PI. LXXII, fig. 5, to show the gen- 

 eral arrangement of the zocecia and the distribution of the 

 larger cells. 



ANISOTEYPA FISTULOSA Ulrich. 



PI. LXXII, fig. 6-6c. 



Zoarium composed of from one to three layers, each about 

 one mm. in thickness, assuming the form of very irregular, 

 branching hollow stems, from less than five mm. to more than 

 ten in diameter. Inner side lined with a finely wrinkled epitheca. 

 Surface generally smooth, at intervals of three or four mm. with 

 clusters of apertures of larger size than the average, which 

 in rare instances are slightly elevated. A few small cells usually 

 present near the centers of the clusters. Apertures regularly 

 arranged, polygonal, commonly hexagonal, varying in diameter 

 from 0.28 mm. to 0.5 mm., in the clusters, nine or ten of the. 

 average size in three mm., separated by comparatively thin 

 partitions. Zooecial tubes curving gently throughout their 

 lenght, not quite direct even at the surface of the layers. Walls 

 thin and flexuous below, but towards the surface they become 

 rather abruptly, but only moderately thickened. Lines between 

 walls of adjoining zooecia sharply marked. Mesopores (?) (small 

 tubes) very rare, only in the groups of large zooecia. Diaphragms 

 with rather large perforations, three or four in each tube, 

 quite commonly observed closing their apertures. 



This fine species is readily distinguished from A. symmetries, 

 (a Chester species) by the thinner walls and in having groups 

 of large cells instead of one or two zocecia of very large size. 



