50 



FOSSIL COAL PLANTS. 



ticated trunk longitudinally striated and bearing obscure 

 impressions of the leal-scars. 



This is a remarkably neat species, and not liable to 

 be confounded with any other lound in this vicinity. It 

 resembles in the variation in the width ol the ribs S. 

 contracta^ Brong., and S~ diploderma^ Corda, but differs 

 from both in the form ot the leaf-scars, which are trapezi- 

 form and angular "in S. di2)loderma^ and in S. contracta 

 much elongated and placed in contractions of the rib. 

 The vascular impressions are also different from those of 

 these species. 



Youngstown, Mahoning county. 



Fig 4.— S. Dentata. 



Trunk ribbed, ribs narrow, alternately 

 1 ightly expanded and contracted, tes- 

 lated by transverse lines, wdiich are 

 I -awn across the ribs along the ujyper 

 Jjorder of the leaf-scars. Leaf- 

 scars closely api)roximated, 

 ovoid, sometimes exhibiting lat- 

 eral angles, terminating below 

 in a small but distinct tooth. 

 Vascular impressions placed 

 high up in the cicatrices, three, in line, nearly punctiform, 

 central largest. Decorticated trunk, obscurely marked 

 with the cicatrices of the exterior, and exhibiting traces of 

 the vascular impressions. Fig. 4, a, represents a leaf-scar 

 enlarged, to show its form more distinctly. 



This species resembles, in many respects, S. alveolaris 

 and S. Knoi'ii, Brong., and, if these species are to be con- 

 sidered identical, it should perhaps be regarded a variety 

 of the same, but I have found the dentation of the leaf-scar 

 a constant character in well marked specimens, and that, 

 with the position of the transeverse line, have led me to 

 consider it distinct. The leaf-scars are sometimes sepa- 

 rated by an interval equal to their diameter. Strongly 



