BRYOZOA. 415 



HETEROTRYPJL SINGULARIS Ulrich. 



PL XXSVU. Bg. 3-8f. 



Zoarinm subramose, at times attaining a thickness of seven 

 cm. Surface smooth, or nearly so, with clusters of cell aper- 

 tures a little larger than the average. Zooecia about nine in 

 two mm., angular and thin-walled in the axial, subeircular in 

 the mature region. There are commonly two or more succes- 

 sions of immature and mature regions. Mesopores of variable 

 size, very numerous, usually angular or subcircular. Dia- 

 phragms developed very irregularly, at times but few in the 

 cortical region and wanting in the axial, at other times about 

 two tube diameters apart in the axial and elosewset in the peri- 

 pheral region. They are commonly horizontal, often concave, 

 sometimes infundibular, and occasionally simulate cystiphragms 

 if they are not of that nature. Acanthopores very numerous, 

 inflecting the visceral cavity so as to give it a petaloid appear- 

 ance. 



The extremely large size of this species, the remarkable de- 

 velopment of acanthopores and mesopores, and irregular char- 

 acter of the diaphragms are its leading features. Some points 

 in its structure leave me in doubt as to this being its rightful 

 position, but for the present it seems best to place it with 

 Heterotrypa. 



Position and locality: Cincinnati group, Wilmington, HI. 



DEKAYIA Edwards and Haime, 1850. 



(PoL Foes, des Ten-. Pal. p. 277.) 

 {For generic diagnosis see p. 371.) 



Extensive remarks upon the position of this genus, as well as 

 full descriptions of a number of species, will be found in my 



Amer. Pal. Bry."* to which I refer the reader. D. aspera, Ed. 

 HL, the typical species, occurs in rocks of the Cincinnati group, 

 near Wilmington, Dl. The specimens are in a bad state of pre- 

 servation, but I had no difficulty in identifying them by means 

 of thin sections. The following species is the only one known 

 from rocks above the Lower Silurian. 



Jour. On. Soc. Sat. Hist. VoL VL pp. 84 and 146-155. 



