560 TRANS. SI . LOUIS ACAD. SCIENCE. 



of the stipe we have: i, solid axis ; 2, common canal or coeno- 

 sarc ; 3, calycles or cellules {hydrotheca) ; 4, nature and orna- 

 ments of tests. 



Some of the Graptolites of the older formations are considered 

 as not having been attached. This may possibly have been the 

 case with some of our cyathiform species in the Niagara, but the 

 evidence is that they were mostly attached by a common root. 

 In one case, all the branches arise from a slender stalk, at the base 

 of which there is a conspicuous, large bulbous root ; in another, 

 the central disc appears to have been attached either directly to a 

 stone or by fibres in the mud. Wheiever the radicle is preserved 

 it is non-celluliferous, and where not preserved the frond appears 

 to have been broken of^'. Only in one species have we a distinct 

 central disc. In those species where the cellules are on one side 

 of the disc, the solid strengthening axis is lateral ; in other cases, 

 where the solid axis is central, the cellules are in two or more 

 rows on the surface. A common canal extends the whole length 

 of the stipes on one side of, or around, the solid axis, and in this 

 the walls of cellules extend to the axis. The cellules are often 

 only represented by serratures along the sides of the specimens, 

 or as oval pits on the surfaces. The surfaces are generally stri- 

 ated. But here the depressions are often caused by the crushed 

 polipary Covering the position occupied by the late individual 

 polypi 



Reproduction of the Gkaptoi ites. 



From the specimens which have been obtained in the Niagara 

 formation in Canada, I have not been able to recognize the mode 

 of reproduction. In 1858, Prof. Hall observed a few graptolitic 

 stipes bearing what he regarded as reproductive cells. Of these, 

 he says, that they appear first as ovate buds upon the margins, 

 extending beyond the ordinary cellules, and enlarging to elon- 

 gated sacs, swollen at extremities, becoming dehiscent, and 

 discharging the ovules. There is very little substance except 

 along the margin, where a filiform extension appeals to rep- 

 resent the solid axis ; numerous fibres also traverse the sacs, 

 and remain attached to the original stipes of the parent. This 

 mode of reproduction as Prof. Hall points out is strong evidence of 

 their Hydroid character, having the nearest analogy to Sertula- 

 riana. In the Niagara formations we often find small specimens 



