484 NEW YORK STxVTE MUSEUM 



Freeh proposes to reject both terms, hydrosome and rhabdosome, hitherto 

 in use for these stipes, as indicating that the latter embrace the whole organism, 

 and to use instead the term hydrorhahd. This term, again, is open to the 

 objection that it suggests the hydrozoan nature of the graptolites. The term 

 polypary, still in common use (also in Monograph of the British Graptolites) 

 implies the close taxonomic relation of the graptolites to the Cnidaria, We 

 shall for this reason here use the term rhahdosome for the colony originating 

 from a sicula and synrhabdosome for the compound colony of the later forms. 

 The rhabdosomes are persons of the second order, being composed of 

 thecae (or persons of the first order), and the synrhabdosomes are persons of 

 the third order, being composed of those of the second order. 



The single hollow cone^ from which the rhabdosome proceeds, was 

 originally termed the radicle or initial point {ex parte), Fvss and Haftorgan. 

 liapworth has introduced the term sicula for it. Holm termed it the first 

 theca. 



Tornquist and Wiman have applied the term connecting canal to that part 

 of the first theca which connects the sicula ^vith the common cavity of the 

 rhabdosome. Holm calls the proximal part of the second theca, which crosses 

 the sicula, the connecting canal. EUes and Wood call this part the crossing 

 canal. 



That aspect of the rhabdosome, in which the sicula is visible in its entire 

 length, is termed the obverse aspect {Siculaseite)^ the other, in which it is more 

 or less covered by the connecting canal, the reverse aspect (Antisiculaseite). 

 That end of the rhabdosome which contains the sicula is most practically termed 

 the sicuiar end, instead of proximal end, and the other the antisicular end. 



The rhabdosome of most graptolites divides into branches. These 

 branches are known as branches, stipes, Arme, Zweige and Grenarne. We 

 call here forms with many branches nmltiramous, forms with few, pauci- 

 ramous. Forms in which the thecae are arranged in one series were called by 

 Barrande and later writers Qnonoprionidian ; those in which they are arranged 

 in two, diprionidian. 



There has prevailed much difference of opinion in regard to the proper 



