566 TKANS. ST. LOUIS ACAD. SCIENCE. 



This fossil is exceedingly common and is o-enerally only repre- 

 sented by bituminous incrustation with no structure visible. 



Fortnation and Locality. — This structure is only found in the 

 upper Niagara shaly dolomites, along Rosseaux creek bottom, 

 east of Hamilton, Ontario. Like many other specimens of the 

 family, it was first observed by Col. Grant. 



Genus RETIOLITES (Barrande). 

 Rele, a net; litlios, a stone. 



"Frond simple(.'') or compound. Stipeselongate, oval, or lan- 

 ceolate, with longitudinal axis and reticulate structure ; margins 

 ornamented with mucronate points. Cellules developed in par- 

 allel ranges on opposite sides of the stipe and in contact with it 

 throughout its entire length." 



Retiolites venosus (Hall). 

 Plate I. Fig. 2. 



(Palaeontology of New York, vol. ii., 1852.) 



I have only seen one specimen of this species. The serrte are 

 arranged alternately on both sides of the stipe at about one milli- 

 metre distant from each other, and form an angle with the stipe 

 of about 45 degrees. They have a length of about two millime- 

 tres. The portion of the stipe obtained is about five centimetres 

 long, and from two to three millimetres wide. The substance 

 between the serrae (which is always very thin) is wanting, but the 

 specimen is easily recognized by the peculiar serrae. 



Formation and Locality. — This fossil occurs in the Clinton rocks 

 at Hamilton, Ontario, and was obtained by Col. Grant. 



Genus DENTROGRAPTUS (Hall). • 



Dendron, a tree; grapho, 1 write. 



(Can. Organic Hemains, Dec. ii., 1865.) 



"• Frond simple or aggregate, consisting of a strong footstalk, 

 which is sometimes furnished below with a distinct root or root- 

 like bulb, and above is variously ramified and subdivided into 

 numerous branches and branchlets, which are slightly divergent, 

 the whole producing a broad, spreading, shrub-like frond (fronds 

 sometimes flabellate .'') ; branches celluliferous on one side; cel- 

 lules appearing as simple indentations on the surface, and some- 

 times distinctly angular, with denticles conspicuous. In some 

 specimens the cellules are indicated by prominent pustule-like 



