GRAPTOLITES OF NEW YORK, PART 2 



31 I 



234 



sometimes gently convex in the distal parts and frequently slightly concave 

 in the sicular region ; attaininga length ol 70+ mm, increasing from an initial 

 width of .5 mm very gradually to one of .9 mm to 1 mm and hence apparently 



of uniform width ; diverging at an angle of 325" to 330". Sicular extremity 

 rounded, with short, blunt virgella and lateral spines ; short mesial spines 

 continuing- to the fourth or fifth theca on either side. Sicula not 

 observed. Four primary thecae develop alter- 

 nately and instead of growing horizontally out- 

 ward as in most Dicellograpti, the)- grow 

 obliquely upward and outward thereby pro- 

 ducing a short biserial portion and suggest- 

 ing a Dicranograptus | see under " Remarks"]. 

 The Dicranograptuslike aspect is still in- 

 creased in some specimens by the acute axil 236 



1 „ 1 • 1 1 • Fie. 234-36 Dicellograptus moffat- 



and a "Web whlCIl COnneCtS the SOmetimeS en sis var. a lab amen sis nov. Fig. 234, 235. 



Sicular portions showing acute axil and * web. 

 1 1111 1 11 r . 1 i r ,1 Fig. 236. View of mature portion of branch, very 



subparaliel dorsal walls 01 the bases 01 the unsatisfactory but the best obtainable. X5 

 branches [see fig. 234]. The thecae number quite constantly 10 in 10 mm 

 with but slight variation ; the ventral walls of their free parts are strongly 

 convex, at least in the initial part of the rhabdosome ; for the thecae of the 

 more distal parts have not been seen in profile in any of the specimens, 

 thereby indicating that the profile line of the thecae did not lie in the 

 intersecting plane of the branches. The apertural parts of the thecae are 

 introverted and opening into pouchlike excavations, which occupy between 

 one third and one half the width of the branch. 



Position and locality. In the upper Trenton shaly limestone near 

 Pratt's Ferry, Bibb co., Ala. where it is the most striking of the graptolites. 



Remarks. We consider this form as most nearly related to D . mof- 

 f a t e n s i s Carruthers, which it most approaches in the general form of the 

 rhabdosome and of the thecae, but from which it differs in the expansion 

 of the branches — those of 1 ) . moffatensi s beginning narrower while 

 expanding more rapidly and to a greater width — and the spinosity of the 

 earliest thecae in our material. The straight and rigid branches of a la- 



