SUPPLEMENT. 591 



GENtJS RaSTRITES (Barrande). 



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 

 " 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 thei 

 " Graptolite schists, constituting the base of our upper division. One of these fouf 

 " 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 state 

 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; 



f PALiEONTOLOOY III.] 66 



