RADSTOCK SERIES OF THE SOMERSET AND BRISTOL COAL FIELD. 357 



Of Neur. cordata, Brongniart only figured a single pinnule, which in its 

 form closely resembles the pinnules of Neur. Scheuchzeri. The type of Neur. 

 cordata appears to be lost, but Zeiller has discovered in the Museum at Paris 

 many other specimens named Neur. cordata by Brongniart himself; these, 

 however, embrace two species. Some of them are the true Neur. cordata as 

 figured by Brongniart and others, are identical with the plants named Neur. 

 acutifolia, Brongt., and Neur. angustifolia, Brongt. Zeiller has very kindly 

 sent me a specimen from the mines of Alais, Grand' Combe, of the plant he 

 identifies as the true Neur. cordata, Brongt. With this before me there is no 

 difficulty in recognising Brongniart's Neur. cordata as essentially distinct from 

 Neur. Scheuchzeri, with which, as will be presently seen, must be united Neur. 

 acutifolia, Brongt., and Neur. angustifolia, Brongt. In Neur. cordata the veins 

 are not nearly so close to each other as those of Neur. Scheuchzeri, and in 

 addition to this the characteristic hairs of Neur. Scheuchzeri are absent from 

 Neur. cordata; — even on specimens of Neur. Scheuchzeri where, through 

 imperfect preservation, the hairs are not visible, the nervation is a sufficiently 

 distinctive character by which to distinguish the two species. 



The nervation of Neur. Scheuchzeri, enlarged three times, is shown on 

 Plate XXIII. fig. 2. The hairs are omitted from this figure to avoid confusion. 

 It will be observed from this drawing that the veins usually divide four times, — 

 the first dichotomy being close to the midrib, the second and third dichotomy 

 carry the veins to about midway between the central vein and the margin of 

 the pinnule, and the arms of the fourth dichotomy extend from this point to 

 the edge of the pinnule. A fifth dichotomy is but rarely observed, and equally 

 rarely do its veins only divide three times throughout their course. 



An enlarged drawing, to show the bristle-like hairs, is given at fig. la. 

 These usually lie obliquely to the veins, imparting to the pinnule a dictyopteroid 

 appearance, which has given rise to Romer's Dictyopteris cordata and Dicty- 

 opteris Scheuchzeri. 



On the original specimens of Neur. Scheuchzeri the presence of the hairs 

 appears to have escaped Hoffmann's observation, or had been effaced through 

 imperfect preservation, but, from his description of the plant and the accom- 

 panying figures, the identification of the specimens occurring in the Radstock 

 Coal Field with Hoffmann's Neur. Scheuchzeri appears to be correct beyond 

 doubt. 



Zeiller has examined the types of Neur. acutifolia and Neur. angustifolia 

 which originated from "Camerton" and "near Bath," and "Wilkesbarre in 

 Pennsylvania," and has observed on them the characteristic hairs, though 

 Brongniart in his description of the two species does not indicate their exist- 

 ence. These two supposed species do not differ from each other except in the 

 outline of the pinnules, which is not of sufficient value for specific distinction, 



