THE HEDERELLOIDEA — ^BASSLER 59 



HEDEROPSIS TYPICALIS, new species 



Plate 14, Figures 2-6 



Zoarium incrusting fenestellid Bryozoa and other organic objects, 

 formed of robust cylindrical tubes averaging 3 mm, in length and 1.3 

 mm. in width, budding at an angle of 45°, with 3 to 4 in 5 mm., and 

 branching at intervals of 5 mm. and 45° angle. The tubes are 

 attached by only a small portion of their basal surface and in budding 

 often grow over each other so as sometimes to form a composite colony 

 of a centimeter or so in thickness. Apertures large, open, terminal, 

 exhibiting on their basal side the characteristic septum and the trans- 

 verse partitions. Occasionally the zoarium becomes freed of the 

 object upon which growth started, in which case it may be clearly 

 noted how one zooecium serves as a central tube giving rise alternately 

 on each side to the usual zooecia, which in turn bud at intervals to 

 form a central tube of a new branch. Both upper and under sides 

 of the tubes are strongly wrinkled. 



Occurrence. — Onondaga (Upper Jeffersonville Mm.esione-S'pirifier 

 acuminatus bed) : Falls of the Ohio. 



Cotypes,—\].^.'NM. No. 54093. 



HEDEROPSIS RAASCm. new species 



Plate 14, Figure 1 



Tliis well-developed species shows considerable resemblance to the 

 H. magna group of Hederella, but the interior of the tubes exhibits 

 the characteristic basal carina of Hederopsis. The zoarium incrusts 

 brachiopod shells, ramose Bryozoa, and other organisms indiscrim- 

 inately, forming colonies of several square centimeters in size, com- 

 posed of short, broad branches arising rather regularly at intervals of 

 5 mm. or less at an angle of about 60°, each starting with a single tube 

 that buds to the right and left alternately several times before a new 

 branch arises. This arrangement is rather marked when the growth 

 is regular. The zooecial tubes average about 2.5 mm. in length and 

 0.7 mm. in width, budding at an angle of 25°. The apertures are 

 terminal and more rounded than usual. The characteristic basal 

 septum is easily distinguished on the better-preserved tubes. Surface 

 ornamentation of rugose wrinkles with a faintly pitted or porous 

 structure on all the walls. 



Although closely related to the genotype, this species may be 

 easily distinguished by its much smaller zooecial tubes and different 

 method of branching and budding. The specific name is in recognition 

 of the work of Gilbert Raasch upon the Milwaukee Devonian section. 



Occurrence. — Middle Devonian (Milwaukee limestone, Lindwurm 

 member): Milwaukee, Wis. 



Holotype.—U.S.'N.M. No. 57530. 



