480 



NEW YORK STATE MUSEUM 



Diplograptus mucronatus Clark. Geol. Mag. Ser. 4. 



1902. 9:498 

 Lasiograptus mucronatus Weller. Geol. Sur. X. J. Pal. 



1902. 3:52 

 Lasiograptus mucronatus Dale. U. S. Geol. Sur. Bui. 



242. 1904. p.33 



Diagnosis. Synrhabdosome apparently composed of 

 small number of rhabdosomes ; 8 being" greatest number of 

 rhabdosomes and 15 that of bases of nemacauli observed. 

 Rhabdosomes slender, of lax appearance, with very thin 

 periderm; attaining a length of 35+ mm; 1 mm wide at 

 the sicular extremity and growing within the space of 8 mm 

 to full width, which as a rule is about 2 mm, but may rise 

 to 2.5 mm and is maintained to the truncate 

 antisicular extremity. Sicular extremity 

 rounded ; sicula small, apparently not longer 

 than 1.2 mm ; furnished with two filiform 

 apertural processes, one of which (the vir- 

 gella) lies in the direction of the axis. 

 Thecae numbering 8 to 10 in 10 mm (20-26 

 in 1 inch), slender, overlapping not more 

 than one half, inclined at low angle (20-30°), 

 with straight to concave outer margin which 

 in the last distal third is extended outward 

 horizontally and produced into the main 

 fibers of the outer meshwork. The aper- 

 tural margin is horizontal or even receding, 

 often concave ; the apertural excavation 

 long triangular, one third the transverse 



457 



majority 



Fig. 456-57 Lasio- 

 graptus mucrona- 



Typical 'appearance 4 of width Of tllC l'lial k1 I >S0 1UC aild half till' 

 rhabdosome. Kig. 457 



fhowhTg of ch» h ract d c°r som of length of the theca. The outer meshwork 



Sicular end and traces of . 



ledges. x 5 J s very delicate, hence lost in the great 



jcimens, where but the thicker bases of the main fibers arc 



