32 PROCEEDINGS OF THE NATIONAL MUSEUM vou 87 



branch at such an acute angle that they often remain m contact with 

 it. Although much like H. cirrhosa Hall, 1881, H. canadensis has 

 smaller dimensions. 



Occurrence. — Middle Devonian (Onondaga): Port Colbprne, Ontario 

 (Decewville limestone) ; vicinity Ann Arbor, Mich, (drift). 



Plesiotype.—U.S.'N.M. Nos. 52961, 87898. 



HEDERELLA SILURIANA, new speciea 



Plate 13, Figure 3 



The type and only known example of this, the oldest known species 

 of the Hederelloidea, incrusts a brachiopod, Protothyris didyma 

 (Dalman), from the Silurian of Gotland, and at first sight seems to 

 represent a well-developed Stomatopora. Closer examination shows 

 it is an infrequently branching Hederella with short zooecial tubes of 

 about the same dimensions as in H. rectifurcata. The typje consists 

 of several overlapping branches, but a single one exhibits branching 

 at a right angle and 2 mm. intervals, with very short zooecial buds 

 1 to 2 mm. long, 0.4 mm. in diameter, arising 3 mm. apart on the same 

 side of the branch at nearly a right angle. More careful comparison 

 with H. rectifurcata will show other differences, such as the extreme 

 angularity of branching and budding in the latter. 



Occurrence. — SUurian (Gotlandian): Island of Gotland (probably 

 KUntehamn). 



Holotype.~V. S.lsl.M. No. 93954. 



HEDERELLA COLBORNENSIS, new epeciea 



Plate 7, Figure 1 



Associated with the genotype, H. canadensis, at Port Colborne and 

 closely simulating it in size, this new species differs in the more strag- 

 gly arrangement of the branches and the longer and more infrequently 

 budding zooecia. Here the general zooecial arrangement is much as 

 in H. vagans, but all of the dimensions are smaller and the zooecia 

 themselves consist of elongated tubes budding from the main ax-is in 

 a decided curve at an acute angle. Branching irregular but usually 

 about 4 mm. apart at 60° angle. Length of zooecial tubes about 

 1.25 mm.; width 0.3 mm.; 4 to 5 zooecia in 5 mm. 



Occurrence. — Onondaga (Decewville limestone): Port Colborne, 

 Ontario. 



Holotype.—V.S.'^.M. No. 87986. 



HEDERELLA CONCINNA, new species 



Plate 7, Figures 10-15; Plate 15, Figure 2 



A delicate species resembling H. canadensis in general size and 

 zoarial form, but differing in that the zooecial tubes are longer and 

 arise more regularly from the axis at shorter distances and at such a 



