DESCRIPTION OF SPECIES. . 61 



Pseudodanaeopsis nervosa, spec. nov. 

 Plate XXXI, Figs. 1,2. 

 Frond pinnate. Principal rachis strong, prominent, and rigid. Pinnules suboppo- 

 site with a strong, rather flat middle nerve, attached by the entire width of the ex- 

 panded base, slightly decurrent in the middle and lower pinnules, and more so in the 

 upper ones, which are obliquely attached and united at base, while the lower pinnules 

 are remote and separate to the base, and go off under an angle approaching a right 

 angle. Middle nerve tapering gradually to the summit of the pinnules, broad and 

 rather flat. Lateral nerves very strong and distinct, departing both from the midrib 

 and from the principal rachis at the base of the pinnules on the lower side. Those 

 from the midrib go off at an acute angle, and curve strongly outwards to meet the 

 margin of the pinnules. They fork near the midrib or at various distances from it, 

 sometimes not until the margin is nearly reached. Those that fork near the midrib 

 fork again one or more times. All anastomose very regularly near or at the margins 

 of the pinnules. 



In this plant also the lateral nerves go off from the midrib at some dis- 

 tance from one another, so that the nervation is rather open. The lateral 

 nerves fork very variously, some fork near the midrib, and these usually 

 fork again one or more times; others do not fork until the middle of the 

 space between the midrib and the margin is reached, and others again fork 

 only near the margin. All anastomose close to and usually on the margin of 

 the pinnules. The nervation is very distinct, for the lateral nerves often ap- 

 pear on the shale when there is no trace of the leaf substance of the plant, 

 and we thus, have a skeleton of the nerves. This is seen in Fig. 2, on the 

 right-hand side of the specimen, where the lateral nerves at the bases of the 

 pinnules leave their imprints, while there is no trace of the pinnule itself. It 

 will be noted that this plant is quite close to the normal form of Danaeopsis, 

 both in the general character of the frond and in the nervation, which is less 

 freely anastomosed than that of the preceding species. The constant union 

 of the branches of the lateral nerves at the margin of the pinnules is a fea- 

 ture, however, not found in Danaeopsis, though occasional anastomosis 



occurs in it. 



Certain forms described by Professor Newberry, from Los Bronces, 

 Sonora, in the report of Captain Macomb, before mentioned, resemble in 

 some respects this plant. 



On plate viii, figs. 2,2a, Professor Newberry gives a very large plant, 

 with the aspect of a Tanaeopteris, or rather Macrotaeniopteris, which he 



