54 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 8t 



HEDERELLA MICHIGANENSIS. new speclea 



Plate 10, Figures 1, 1', Plate 12, Figure 5 

 The several zoaria upon which this species is based are clearly 

 related to the other members of the H. magna group, but they differ 

 ill that the branching is less regular, the zooecia are longer and emerge 

 usually at a greater angle, and the microscopic dimensions although 

 large for the genus are all smaller. In H. michiganensis the zooecial 

 tubes average 2 mm. in length, their diameter is about 0.8 mm., and 

 they issue from the main axis at intervals of their own length so that 

 usually 2 occur in a distance of 5 mm. The details of the surface 

 are rather similar to the other members of the group. 



Occurrence. — Middle Devonian: Lake Shore at Bay View, Emmet 

 County (co types) (Upper Gravel Point limestone). Thunder Bay 

 River (Norway Point formation), Rockport quarry, Alpena Coimty 

 (cotype) (Upper Ferron Point formation), 1.6 miles north of Nor- 

 wood, Charlevoix County (Petoskey formation), ji mile northwest 

 of Bolton, Alpena County (Alpena limestone), all in Traverse group 

 of Michigan; Falls of the Ohio (Sellersburg limestone). 

 Cotypes.— V.S.N. M. Nos. 87941, 93966, 94591. 



HEDERELLA ROBUSTA, new species 



Plate 10, Figure 2; Plate 12, Figures 6, 7 



The robust colony in this species is occasioned by the very frequent 

 brandling of zooecial tubes, which in their general form and size are 

 similar to those in other species of the group. Branching occurs at 

 rather regular intervals of about 6 mm. and an angle of 45°, and the 

 initial zooecium of a branch gives rise by frequent budding to 

 5 or 6 tubes before a new branch commences. The zooecia after 

 leaving the parent tube vary in length according to age, but the 

 average mature one is at least 3 mm. long and 1.2 mm. wide, with 

 2 usually occurring in 5 mm. Budding is usually at an angle of 30°. 

 Surface very finely annulated with slightly coarser ridges at intervals. 

 Although similar to H. hibbardi, the growth is more robust, tubes are 

 larger, and branching more distinct. 



Occurrence.— Middle Devonian: Norway Point Dam (holotype) 

 (Norway Point formation) and other localities in Alpena County 

 (Genshaw and Ferron Point formations), Iji miles northeast of Bay 

 View and 1.6 miles north of Norwood, Charlevoix Coimty (Petoskey 

 formation), y, mile northwest of Bolton, Alpena County (Alpena 

 limestone), all in Traverse group of Michigan; IK miles southeast 

 of Last Bethany (Kashong shale) (paratype) and 3 miles west of 

 East Bethany, N. Y. (paratype) (Centerfield shale); Thedford, 

 Ontario (Widder shale). 



Holotype and paratypes.—V.S.NM. Nos. 87946 93961 93964 

 93965, 93968. ' ' ' 



