562 



TRANS. ST. I.OUIS ACAD. SCIENCE. 



{b) "Cellules on two sides near base, sti- j 



pes dichotomous above, with a row [.Djcanograptus. 

 of cells only on the outer margins 1 

 of each division." J 



" Solid axis eccentric or sub-exterior, with 

 cellules developed in parallel ranges on 

 opposite sides of the stipe, and in contact 

 throughout their entire length." 



(a) "Known only as separate stipes 



with reticulate test." 

 (^) "Occurring as simple stipes and 

 compound fronds; test smooth." 

 II. 



Retiolites 



Retiograptus. 



Dendrograptus. 



Callograptus. 



I 

 ^■Calyptograptus 



Species having a common trunk or stem, or growing in sessile groups of 

 stipes, from a common origin, without distinct bilateral arrangements 

 of the parts." 



I. Cellules in a single series on one side of the 

 stipe or branches, and situated along one 

 side of common canal. 



(a) "Branching free (not connected by ^ 

 transverse bars) ; cellules in contact 

 or closely arranged." 

 {b) "Branches infrequently connected 

 by transverse bars." 



(c) "Stipes and branches more or less ^ 

 regularly united in a reticulate > Dictyonems 

 frond, without elongate stem." ) 



(d) Stipes and branches touching or1 

 overlapping in a reticulated man- 

 ner, but without or with very few 

 transverse bars. (Spencer.) J 



(e) Stipes and branches reticulated re-") 

 gularly without transverse bars, 1 

 and united at base in a long stem J^Rhizograptns. 

 terminating in a bulbous radicle, j 

 (Spencer.) J 



(/) Stipes and branches free, numerous! 

 rudimentary branchlets on both 

 sides, and also spine-like cell-deiita- 

 cles. (Spencer.) j 



2. Cellules on more than one side( .') or over ^ 



the surface; axis central (as observed > Inocaulis. 

 bv Spencer). J 



III. 

 Slender cylindrical branches, with tubular cellules ^ 



arranged in a single (or in double.') series; eel- > Rastrites. 

 lules not in contact in any part of length." ) 



Acanthograptus. 



