no. 1769. FOSSIL PLANTS OF THE POTOMAC GROUP BERRY. 639 



tions in the methods of preservation. At first glance the rachis ap- 

 pears to have boon wide and ribbon-like, but this was not the case. 

 The segments are inserted on the upper surface of the rachis in con- 

 formity with the generic diagnosis, and in one of the specimens the 

 lateral veins of opposite sides approach to within 1 mm. of each other, 

 being separated by a slightly raised ridge. Vent rally it is seen that 

 the large rachis is flattened and during or since fossilization small 

 fragments of the inner margin of the segments overlying the rachis 

 are more or less flaked off, exposing in places the broadly flattened 

 rachis. In another specimen the segments of one side are still at- 

 tached centrally to the top of the rachis, which is flattened and pushed 

 over in the opposite direction, the segments of the other side being 

 broken off proximally, again giving the appearance of a broad, flat 

 rachis. In the final report the writer will show photographic repro- 

 ductions of a number of these forms with cross-sections illustrating 

 the manner of fossilization, and showing conclusively the correctness 

 of the foregoing statements. 



Occurrence. — Patuxent formation, Fredericksburg, Virginia. — 

 Arundel formation, Langdon, District of Columbia. 



Collections. — U. S. National Museum. 



THE GENUS SAPINDOPSIS OF FONTAINE. 



This curious genus was founded by Fontaine ° in 1890, and referred 

 to the Family Sapindacese of the Order Sapindales. It was charac- 

 terized as follows: 



Leaves pinnate, both odd pinnate and abruptly pinnate; terminal leaves usually 

 more or less united at base; upper pairs of leaves decurrent, funning a wing on the 

 common stem, the wing lessening in width on the pairs in descending; leaves mostly 

 opposite in pairs, sometimes subopposite; the lowest pairs lack the wing, and are some- 

 times short-petioled; leaves thick, with dense and often glossy epidermis, elliptical 

 or lancet-shaped, with a strong prominent midrib, which extends with slight diminu- 

 tion to the tip of the leaf; lateral nerves going off at a large angle, and uniting more or 

 less completely near the margin to form a series of arches; the lateral or primary nerves, 

 as seen on the lower side of the leaves, strong and prominent, but on the upper side, 

 owing to the thickness of the leaves, generally indistinct; the ultimate reticulation is 

 strong, and forms a series of rather large, irregular, polygonal meshes. 



Sapindopsis is an important (dement in the flora of the uppermost 

 member of the Potomac group, the Patapsco formation, to which the 

 genus in exclusively confined, with the single exception thai Sapin- 

 dopsis variabilis has been recorded in the nearly homotaxial Fuson for- 

 mation of Wyoming. No specimens of Sapindopsis are known from 

 either the Patuxent or Arundel formations or their equivalents in 

 other parts of North America. It is true that Professor Fontaine 

 described Sapindopsis cordata from Fredericksburg, Virginia, but this 



a Fontaine, Monogr. F. S. Geol. Surv.. No. L5, 1890, i». 296. 



