74 Forty-fourth Report on the State Museum. 



of strong longitudinal ridges, and interapertural pits ; its size and 

 thickness will easily distinguish it from any other species of the 

 Lower and Upper Helderberg and Hamilton groups, at present 

 known, with the e:f ception of S. ovata, and it may be distinguished 

 from that species by the more decidedly ovate form of the apertures 

 and in the posterior portion of the aperture being the narrower, the 

 equally elevated peristomes and the wider space between the rows 

 of apertures. 



Formation and locality. — Hamilton group, West Williams, 

 Province of Ontario, Canada. 



Stictopora limata. 



Stictopora limata, Hall. Palaeontology of New York, vol. vi, p. 250, pi. Ixi, 



figs. 14-16, 1887. 



* 4f- ^ * % -Jf ^ # * 



This species has a slight resemblance to the ordinary forms of 

 S. incisurata; from those forms having broad longitudinal ridges, 

 it may be distinguished ty the more slender frond, its more rigid 

 appearance, comparatively more infrequent bifurcations, smaller 

 cell apertures, and their more regular disposition in parallel, 

 longitudinal rows ; from S. suhrigida it may be distinguished by 

 the somewhat wider branches, larger oval cell apertures, which are 

 not pustuliform. The cell apertures of that species have a 

 diameter of about .10 mm. ; are circular and pustuliform ; very 

 nearly the same features will distinguish it from S. angularis. 

 From S. recta it may be distinguished by the somewhat wider 

 branches, smaller and more distant cell apertures, fewer ranges of 

 apertures on a branch; much wider longitudinal ridges, and the 

 absence of nodes on the ridges; from S. bifurcata by the more 

 distant bifurcations, fewer ranges of apertures on a branch, and 

 much wider longitudinal ridges, and the absence of minute nodes ; 

 from Ptilodictya parallela by the smaller cell apertures and the 

 much stronger longitudinal ridges ; from Stictopora rigida and 

 >S^. crescens of the Upper Helderberg group by the much smaller 

 and comparatively more distant cell apertures. 



Formation and locality. — Hamilton group, Darien Centre, N. Y, 



