no.1769. FOSSIL PLANTS OF THE POTOMAC GROUP BERRY. 643 



the rachis. Certain specimens show all of the leaflets petiolate, a 

 feature much emphasized in specimens collected recently on Stump 

 Neck, Maryland, in which the petioles are 3 to 4 cm. in length. The 

 leaflets in this species are much oftener petiolate and lacking in the 

 winged rachis than in Sapindopsis variabilis, in these features closely 

 resembling the leaves of the modern Matayba apetala in which the 

 rachial wings are vestigal. Leaf substance thick and leathery, epi- 

 dermis 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 11) pairs, blanching 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 areola? where visible. 



This species is very common at certain localities within the Pa- 

 tapsco formation, as, for example, on Stump Neck, in Charles County, 

 Maryland, 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 collections have been made without dis- 

 closing 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 Sapindopsis 

 variabilis are slight, since both are variable and the larger forms of the 

 latter are quite as large as the smaller forms of Sapindopsis magni- 

 folia. In the Potomac they are found in association at all the locali- 

 ties where either occur, and the smaller species is usually the most 

 common as if Sapindopsis 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 Sapindopsis variabilis 

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

 disparity in size between the two. There are certain other differ- 

 ences which appear to be constant. These are the thicker relatively 

 longer leaflets of Sapindopsis magnifolia with less numerous and some- 

 what more ascending secondaries which are not connected distally by 

 relatively flat arches. The writer includes under this species the 

 Sapindopsis tenuinervis of Fontaine, recorded from the localities 

 near Brooke, Virginia, and from Fort Foote, Maryland. The only 

 apparent ground for its erection was a fancied difference in vernation 

 based chiefly on a more slender midrib and more remote leaflets, both 

 characters which are seen to be variable and altogether unreliable 

 as soon as any number of specimens are compared. 



