442 NEW YORK STATE MUSEUM 



which is still increased by an inflation of the nemacaulus that already begins 

 within the rhabdosome and shows a distinct inclosed virgula. 



In its greater length, parallel margins, smaller width and more distant 

 thecae this form has the characteristics of the variety 1 i n e a t u s of C . 

 antiquus distinguished lately in the Monograph of British Graptolites. 



cryptograptus Lapwortli. 1880 

 Lapworth defines this genus as follows : 



Polypary diprionidian, with attenuated punctate test, subparallel mar- 

 gins, and concavo-convex (?) section. Hydrothecae inclined; lower wall 

 straight or slightly arcuate, outer third forming a distinct excavation, the 

 upper sinus of which is mucronate and oblique ; outer wall very short, per- 

 pendicular ; aperture very oblique, lying wholly within the ventral margin 

 of the polypary. 



Type Diplograptus (Cryptograptus) tricornis, Can*. 

 There is no doubt that this genus represents a well defined group, which 

 though known only by a few species, is easily recognized and has characters 

 which clearly separate it from both Diplograptus and Climacograptus, 

 though with both of the latter it has also some features in common. The 

 most notable of the former characters are the thin periderm of the rhabdo- 

 some — on account of which the latter lacks the gloss of the other thick 

 tested graptolites and as a rule has a somewhat hazy appearance — and the 

 deep excavation of the outer margin of the thecae. 



The writer's material of the genotype shows that the apertures of the 

 sicula and of the thecae, are provided with stout rings [see text fig. 415]. 

 These and the rather strong nemacaulus served evidently to strengthen the 

 otherwise frail periderm. 



A remarkable feature are the widely different aspects which the rhab- 

 dosomes of Cryptograpti are able to present according to the direction of 

 compression ; most notable among these is the difference between the 

 frontal and lateral views. The frontal aspect is broad and presents per- 

 fectly straight, parallel lateral margins, while the other, on account of the 

 small inclination and dee)) excavation of the outer margin of the thecae is 

 much narrower and deeply indented. 



To this difference of aspect several errors are evidently due. Thus I 

 have become convinced from the study <>l the genotype thai the two tonus 



