472 Systematic Paleontology 



joining the lamina of the leaflet next below at the point of juncture of 

 its inner margin with the rachis. Certain specimens show all of the 

 leaflets petiolate, a feature largely emphasized in the specimen figured 

 from Stump Neck showing three terminal leaflets with petioles 3 to 4 

 cm. in length. The leaflets in this species are much oftener petiolate 

 and lacking in the winged rachis than in S. variabilis in this particular 

 closely resembling the modern Matayha apetala in which the rachial wings 

 are vestigial. Leaf substance thick and leathery, epidermis firm and 

 glossy. Leaflets commonly subopposite, often markedly so, forming an 

 acute angle with the rachis. Midribs stout and prominent below. 

 Secondaries slender, only seen on the under surface of the leaflets and 

 even then made out with difficulty, 8 to 10 pairs, branching from the 

 midrib at a rather wide angle especially in the central part of the leaf; 

 the angle is more acute basally, curving upward ultimately to join a 

 short branch of the secondary next above. Tertiaries fine, forming 

 lax subrhombic areolae where visible. 



This species is very common at certain localities within the Patapsco 

 formation as for example at Stump Neck in Charles County, although 

 at other outcrops of this same formation it has not been detected. This 

 is notably the case in the Federal Hill deposits from which large collec- 

 tions have been made without disclosing a single specimen. Evidently 

 the species was local in its distribution which is emphasized by its total 

 absence in any other Lower Cretaceous deposit either here or abroad. 



The grounds for the separation of this species from 8. variabilis are 

 slight since both are variable and the larger forms of the latter are quite 

 as large as the smaller forms of 8. magnifolia. In the Potomac they are 

 found in association at all the localities where either occur and the 

 smaller species is usually the most common as if 8. magnifolia represented 

 the occasional more robust forms of that species. On the other hand 

 the latter has not been detected in the abundant remains of 8. variabilis 

 found at Oak Creek, Wyoming, and there is commonly considerable dis- 

 parity in size between the two. There are certain other differences 

 which appear to be constant. These are the thicker, relatively longer 

 leaflets of 8. magnifolia with less numerous and somewhat more ascend- 



