130 GEOLOGY. 
botany. As, however, the limits of the genera of fossil plants when first established are in a 
great degree provisional, and each discovery of new species is liable to modify the previous 
grouping, and necessitate a revision of generic definitions, it would tend to retard rather than 
advance. scientific progress to insist upon the establishment of new genera for species which, 
however closely allied to those before described and generically grouped, should present some 
characters incompatible with former generic descriptions. 
The genus Cyclopteris has been the conventional receptacle of a large number of plants 
which have in common a general flabelliform, orbicular, or heart-shaped outline; are without 
a median nerve; their fine and crowded nervules radiating from the base to the margins, and 
dichotomously forked. Among these are some species which, if we had the living plants before 
us in fructification, we should probably find to be somewhat widely separated. Some of them 
are doubtless the basal and abnormal fronds of highly decompound ferns like those of Allosorus 
sagittatus.* Others were the cauline pinnules of Newropteris; and still others were simple 
stipitate species like the common living Camptosorus rhizophyllus and various other simple- 
fronded ferns. Brongniart has separated from the others those which he supposes to have 
been attached to the stipes of Newropteris—such as C. obliqua, C. orbiculata, C. dilitata— 
under the name of Nephropteris, and leaves as types of his genus Cyclopteris, C. reniformis, C. 
trichomanoides, C. digitata, C. Huttoni, &c.t My observations in the different species of 
Cyclopteris found in the Coal measures have led me to the same conclusions, and to infer that 
nearly all the large solitary orbicular, cordate or auricled fern fronds should be regarded as the 
basilar or rachidian folioles of Newropteris. I have found several species of that genus so 
generally accompanied by particular species of Cyclopteris that I have been compelled to regard 
them as portions of the same plant. So marked is this companionship that I have been inclined 
to doubt whether any of the simple leaved species of Cyclopteris of the Coal measures should 
be retained in that genus. 
Locality and formation.—Bands of clay in beds of lignite between the base of the Cretaceous 
series and the summit of the variegated marls near the Moqui villages. 
PECOPTERIS. Brong. 
PECOPTERIS CYCLOLOBA, (u. sp.) 
Plate II, figs. 3, 4 and 4a. 
P. fronde bipinnatifida v. tripinnatifida; pinnis longis linearibusque, pinnatifidis; pinnulis 
brevissimis semirotundis v. suborbiculatis vel oblongis, obstusisimis, contiguis, sepe inequalibus, 
superioribus majoribus; nervis pinnatis valde notatis (3 utrinque lateris) simplicibus vel rarius 
furcatis. 
This is an exceedingly pretty species, of which the details of structure are well shown in 
my specimens, though they are small. The size and form of the frond, as well as its range of 
variation, will require a greater amount of material for their elucidation. 
The pinne are very long and slender, as shown in the figure given of a portion of the upper 
parts of the frond; the pinnules are usually semicircular, or forming more than a half circle; 
when, as sometimes happens, they are opposite, the pinne have a peculiar beaded appearance. 
The upper pinnules are frequently largest. 
| Although this plant is new, it is not without value in the determination of the geological 
position of the rock in which it occurs. It is most nearly allied to the Pecopterides of the Oolite 
of Europe, such as P. acutifolia and P. obtusifolia, Lind. and Hutt; P. arguta, Brong; and 
among American fossil plants to P. undulata, Hall.t 
: _ © Geeppert Gatt. Foss. Pflantz. p. 89, pl. VIII and IX, fig. 1. 
+ Dict. Hist. Nat. vol. XIII, p. 65. 
¢ Fremont’s Report, Expedition of 1842 and 1848. 
