CARBONIFFROUS SYSTEM. 
it 
In the next group fossils are very rare, and have been found only at 
three horizons between Po and Thcibo. The 
Plant''beds. lowest horizon is a band of green and greyish- 
green shales, which is exposed on the left bank of 
the Spiti river, about \^ mile above Th^bo. The only outcrop hitherto 
observed occurs under a band of quartzite at the water's edge, and 
during the summer floods is frequently inaccessible. It has yielded 
only poorly preserved plants ; these, however, have been examined by 
Professor R. Zeiller, to whom the writer is greatly indebted for the 
following note sent through Mr. R. D. Oldham: — 
"The specimens collected in Spiti by Mr. Hayden comprise a 
fragment of a simply pinnate frond and numerous pinnulae of 
a fern with cyclopterid venation, which does not appear to dififer 
appreciably from Rhacopteris inaequtlatera, O. Feistmantel {non 
Goeppert sp.) from the Culm of Smith's Creek, Port Stephens, and 
Arowa, New South Wales. I have noticed also a very small fragment 
of a pinna of another fern very similar to Sphenopteridium furcilla- 
tum, Ludwig (sp.), from the Culm or devonian of Hesse-Nassau, but 
the specimen is too fragmentary for specific determination. There are 
also small fragments of a fern recalling Sphenopteris rigida, Ludwig, 
fro.n the same formation, but which are still less fit for definite identi- 
fication. It is difficult to draw any certain conclusion from these 
materials as to the age of the beds in which they occur, yet the 
identity of the fern most largely represented with Rhacopteris inx- 
quilatera from the Culm of New South Wales seems to me sufficiently 
probable to warrant the inference that the beds belong to the same 
horizon as those of Arowa and Port Stephens." ^ 
* " Les ecliantillons recueillis a Spiti par M. Hayden comprennent un fragment 
de fronde simplement pinnee at de nombreuses pinnules d'une Fougere k nerva- 
tion cyclopt^roide, qui me parait ne differer par aucun caractfere appreciable du 
Rhacopteris incBquilatera, O. Feistmantel [non Goeppert sp.), du Culm de Smith's 
Creek, Port Stephens et Arowa dans la Nouvelle-Galles du Sud. J'y ai remarqii^ 
en outre un trfes petit fragment de penne d'une autre Fougere trfes analogue au 
Sphenopteridium furcillatum, Ludwig (sp.), du Culm ou Devonien de la Hesse- 
Nassau mais r^chantillon est trop fragmentaire pour 6tre d^termin6 specifiquement. 
11 en est de mfeme de petits lambeaux de Fougere qui rapellent le Sphenopteris^ 
( 47 ) 
