44 



LOWER PENINSULA. 



Pores large, situated on the lateral edges of the tubes. Diaphragms 

 well developed, irregularly oblique or straight transverse. Found 

 in the Hamilton strata, of Thunder Bay region, near Sunken Lake ; 

 more common in the Hamilton group of Widder, C. W., and in 

 the Hamilton strata of Iowa. 



Plate XVH. — P^ig. 2 gives a surface view of part of a specimen 

 from Widder, C. W. 



LIMARIA STEININGER. 



Synon., CCENITES ElCHWALD. 



Small branching stems or laminar expansions, composed of thick- 

 walled, conico-cylindrical tubules, with transversely compressed 

 orifices, opening obliquely to the surface, surrounded on the outer 

 side by an exsinuated lip, bearing two teeth projecting into the 

 cavity. From the median line of the inner side of the walls, 

 another tooth-like crest projects between the two outer ones. The 

 tubes are connected by lateral pores, and intersected by transverse 

 diaphragms. The diaphragms are regularly found in the thin- 

 walled tube portions, but are rarely developed in tubes with 

 thickened walls. 

 . From Alveolites, Limaria differs only by more conical, stout- 

 walled tubes, of less compressed and more rounded form in the 

 central or basal parts of the polyparia. The number of longi- 

 tudinal crests is in Limaria more restricted than in Alveolites, and 

 rarely exceeds three. The three dentiform projections at the 

 orifices of Limaria are the only structural difference separating it 

 from the genus Cladopora, which has smooth, not crested tube 

 channels ; there are also, however, in species of Cladopora indi- 

 cations of crests, and the generic arrangement of many of the spe- 

 cies in question is more a matter of individual arbitration than based 

 upon any obvious typical difference. 



LIMARIA RAMULOSA, Hall. 



Found in the Niagara group of Lockport, etc. I have not been 

 able to find it in Michigan. Another form of ramulets, which, accord- 

 ing to the denticulated structure of their tube orifices belong to the 



