NicKLEs ANP BAssi.KK.] DIAGNOSES OF GENERA. 21 



The systematic position of the following o-onera, placed provisionally 

 in this family, is uncertain. 



Hedekella Hall (Nicholsonia Davis). 



Zoarium adnate, consisting of a tubular axis, from which the zocecia 

 ])end off alternately to left and right; zooecia annulated and striated 

 transversely and tinely striated longitudinally; apertures terminal, 

 equaling in width the diameter of the zocecia. 



Genotype: Alecto canadensis Nicholson. Devonian. Six species. 



Hernodia Hall. 



Zoarium adnate, consisting of linear series of elongated, annulated 

 zocecia, budded from the sides of preceding zooecia; apertures terminal, 

 equaling in width the diameter of the zooecia. 



Genotype and only known species: Hernodia hunvifusa Hall. Devo- 

 nian. 



Reptaria Rolle (Ptilionella Hall). 



Zoarium adnate, consisting of cylindrical, annulated zooecia in con- 

 tact but not coalescing along their sides, and proceeding in the plane 

 of their host laterally outward from a median line and then upward; 

 apertures terminal, equaling in width the diameter of the zo(Pcia. 



Genotype: Rejptaria stolonifei'a Rolle. Devonian. Two species 



Family IDMONEID^ Busk. 



Zoarium of free or adnate subcylindrical or subprismatic branches; 

 zocecial apertures rounded, more or less elevated, usually arranged in 

 transverse rows on two faces of branches, these two faces sometimes 

 l)eing confluent; dorsal surface of branches without zooecia; small tubu- 

 lar pores may open on either surface of the branches, but more fre- 

 quently on the dorsal. 



Crisinella Hall. 



Zoarium ramose, solid; celluliferous on one face; apertures arranged 

 in rows, alternatel}^ arranged, ascending obliquely from the middle to 

 the margins of the branch; peristomes prominent. 



Genotype and only known species: Orisuia f scroblcidata Hall. 

 Devonian. 



Protocrisina Ulrich. 



Zoarium consisting of narrow, bifurcating branches, celluliferous on 

 one face only; zooecia subtubular, Avith prominent, circular apertures 

 arranged in intersecting diagonal series; on both faces small pores 

 irregularly distributed. 



Genotype and only known species: Protocrisina exigua Ulrich. 

 Ordoviciau. 



