SUPPLEMENT. 
S2i 
Genus Rastrites ( Bar#ande). 
This genus was proposed by M. J. Barrande in 1850, to include certain 
graptolitic forms which he describes as follows : 
“ This polypier is composed of a small, almost linear, very long, and slightly 
“ curved stem, provided with an interior canal forming the communication between 
“ all the cellules. These are disposed upon the convex side of the axis, and make 
u with it a slightly acute angle : they are completely isolated from each other. The 
“ proportion between their length and their reciprocal distance varies according to 
,£ the species. The diameter, in the known species, is always greater than that of 
“ the stem to which they are fixed. 
“ Distribution of species. The Genus Rastrites has hitherto been represented 
“ only by four forms, all belonging to Bohemia : they characterize the mass of the 
“ Graptolite schists, constituting the base of our upper division. One of these four 
“ forms, Rastrites peregrinus , is also found in Saxony. 
“ Relations and differences. It must be observed that there is a very great analogy 
“ between the Genus Rastrites and the Subgenus Monoprion. The only characters 
“ which lead us to separate them are : 1, The isolation and the great space between 
“ the cells composing the polypier, which we call Rastrites ; 2, The great tenuity 
“ of their filiform stems, always more slender than the alveoles which they support.” 
Notwithstanding some slight differences from the generic description 
here given, I have referred the following form to this genus : 
Rastrites barrandi (n. s.). 
Stipe slender, filiform, rigid, slightly curved, and furnished on the concave 
side with numerous, nearly regularly disposed, minute, setiform pro¬ 
cesses or cellules, at the bases of which there is a slight thickening or 
expansion of the principal stipe. Stipe, and cellules or processes, rounded 
in their natural condition. 
The fragment is about two and a quarter inches in length, and in its natural statb 
has evidently been a nearly or quite cylindrical tube, a longitudinal depressed line 
indicating the place of the axis. In this length there are more than forty of these 
minute processes; the stipe just below each one swelling out a little on that side; 
[ Paleontology III.] 66 
