GRAPTOLITES 01" NEW YOUK, I'AKT 1 693 



tural margin noriual on the axis of theca (forming an angle of 150" with axis 

 of branch). 



Position and localities. A single siii-face in the quarry beds (graptolite 

 bed 5, belonging to the zone with D. bifidns) was found to contain this 

 species in numerous specimens. The species has not been rej^orted fi'oni 

 Canada. In Great Britain it occurs in the Upper Arenig of the St David's 

 and Lake districts (Middle and Upper Skiddaw 

 slates), in association with D. bifidus and 

 Diplograptus dentatus. 



Fig. 88 D i d y m o g r a ]) t II s nanus 



Re-marls. This form was originally described ^if."^"'?^- ^o'ti"" of hraneh. Deep 

 by LapAvorth as a dwai'f variety of D . i n d e n - 



tus Hall {I'eete dentatus; see Freeh, Lethaea palmozoica 1:590), with 

 which it agrees in everything except size and number of thecae in a given 

 unit of length. While it is sufficiently distinct to be recognized as a species, 

 its close relationship to I) . dentatus Hall is undubitable. 



Brogger \]or. clt. p.40j records the occurrence of a variety of 1) . denta- 

 tus at Krekling near Christiania. This may also be a D . nanus. 



Didymograptus (Isograptus) caduceus Salter emend. Ruedemann 



Plate 13, flg:ures 6, 7 



Didymograpsus caduceus Salter (^ars). Quar. Jour. Geol. Soc. 1853. 9:87, 



iig.la 

 Didymograpsus caduceus Salter (^ars). Quar. Jour. Geol. Soc. 1863. 19:138, 



p. 137, fig. 13a 

 Graptolites (Didymograpsus) caduceus McCoy. Pal. Geol. Sur. Vic- 

 toria. Prodr. Pal. Victoria, decade 2. 1874. p.30, pl.20. fig.3-5a 

 Tetragraptus bryonoides Hall (D. caduceus Salter) Etheridge jr. 



Ann. and Mag. Nat. Hist. 8er.4. 1874. 14:'i, pi.:'., fig.3, 4 

 Didymograptus gibberulus Nicholson. Ann. and Mag. Nat. Hist, ser.4. 



1875. 16:271, pl.7, fig.3, :^.a, 3b 

 Phyllograptus stella Hopkinson. Quar. Jour. Geol. Soc. 1875. 31:658, pl.34, 



fig.6 

 Didymograptus gibberulus Moberg. Geol. Foren. Stockli. Forli. 1891. 



13:221 



