Contributions to Pala'ontoloriy. 27 



horn-shaped cavit}', upon the concave side of which other bryozoa at- 

 tach. The result of this method of growth is the extension of the ex- 

 panding cup-shaped basal cavit}-, formed b}' the multiplicity^ of brj-ozoa, 

 into a circular-hoi'n shaped cavit}', with the mouth at the posterior end 

 as shown in the illustration. 



The epitheea is thin and concentricall}' wrinkled. The corallites are 

 subequal in size, the larger ones collected into groups. They are thin 

 walled and arranged in diagonal lines, somewhat like the arrangement 

 in IfonticuUpora quadrata. The calices are hexagonal, pol3^gonal, round 

 or otherwise variable in form (though the hexagonal ones seem to be the 

 most common), and measure from 8 to 12 in the space of a line. The 

 larger calices are sometimes gathered into tubercles, while other speci- 

 mens are free from these elevations. Specimens vaiy from l-5th to 

 3-5ths of an inch in length, and from l-6th to l-3d of an inch in width, 

 and appear to have always been free from attachment to other sub- 

 stances. 



This species we separate from all others by its form and method of 

 growth. We regard it as belonging to the class brj^ozoa, because regu- 

 lar calcareous partitions or tabulae are not found in the microscopic 

 sections, and because we believe its method of growth was gemmipar- 

 ous, and that each animal resided in a separate cell. It ma}^ be that 

 the genus Monticulipora belongs to the true polyp corals, and if so, it 

 may be that our species should be arranged in a new genus, but we 

 prefer to leave it in this genus rather than attempt to found another 

 without special study of all the Silurian forms. 



This species is not uncommon on Mount Auburn, at an elevation of 

 about 400 feet above low-water mark at Cincinnati. 



Agelacrinds septembrachiatus, n, sp. (Plate I., fig, 9,) 



[Ety, — Septem, seven; bracMa fits, haying arms.] 



This species is founded upon a single specimen, which was found in 

 the upper part of the Cincinnati Group, near Waynesville, Ohio, and is 

 now in the collection of C. B. D^^ er. Onl}^ a small part of the disk is 

 visible, between the closely wrapped arms, where it appears to be com- 

 posed of very small almost granular plates. 



There are seven very long, strong arms, curved sinistrally, with the 

 smaller ends drawn under as if in the effort of hugging ^'•et more closely 

 together. The plates are about three times as long up and down 

 through the arms as they are in the direction of the length of the arms 

 or across the arms, and they alternately interlock with each other. 



It is distinguished from A. vorticellatus by having seven instead of 

 five arms, and moreover the arms are comparatively longer and strong- 

 er. It is a rare and anomalous species. 



