DESCRIPTION OF SPECIES. 59 



anastomosis of the lateral nerves, but this is not the case with the species of 

 Pseudodanseopsis. They have always the secondary nerves anastomosed, 

 and this is clearly no sporadic occurrence. It is one of the most constant 

 and characteristic features of these plants, which, without it, would certainly 

 be species of Danaeopsis. 



Pseudodauaeopsis reticulata, spoc. nov. 



Plate XXX, Figs. 1-4. 



Frond pinnate. Principal rachis rigid, smooth, and stout. Pinnules alternate, 

 more or less expanded at base and decurrent, attached by the entire base, attaining the 

 dimensions of at least 12 centimeters in length and 2£ centimeters in width, oblong, 

 ensiform or lancet-shaped, having the extremities narrowing, with an elliptic outline. 

 Middle nerve of the pinnules cylindrical, strong, and very sharply defined, gradually 

 tapering to the tips of the pinnules. Lateral nerves very slender, but sharply defined, 

 and immersed in the rather thick and coriaceous leaf-substance of the pinnules, going 

 off from the principal rachis on the lower side of the base of the pinnules, and from 

 the middle nerves under an angle of about 45°, branching sometimes near the point of 

 insertion and sometimes only at a considerable distance from the midrib of the pin- 

 nules, the branches anastomosing several times and finally emerging free at the margin 

 of the pinnules. 



This species has several characters by which it may be recognized at 

 a glance. Its prominent rigid midrib, the thick texture of the pinnules, and 

 their straight, well-defined border cause the pinnules of this plant to leave 

 imprints whieh cannot be mistaken for those of any other species. The 

 pinnules must have been very easily broken off, for they are usually found 

 detached, as represented in Fig. 2. Detached pinnules and fragments are 

 quite common, but specimens showing the mode of attachment are very 

 rare. I could only find a few, after long and persistent search for them. 

 The pinnules in the lower or middle part of the frond seem to have been 

 attached under rather an open angle, as represented in Fig. 1, while those 

 of the upper part appear more oblique and decurrent, as shown in Fig. 4. 

 The nervation is thin and delicate, though very sharply defined, and it is 

 immersed in the rather dense leaf-substance. Some of the specimens occur- 

 ring in a fine-grained shale show the minutest details of the nerves with a 

 perfection not surpassed by the finest lithograph. This was the case with 

 the specimen depicted in Fig. 4, the details of the nervation of which are 

 given in Fig. 4 a, which represents an enlarged portion of the specimen. Fig. 



