AUT. 27 NEW MIDDLE CAMBRIAN FOSSILS EUEDEMANN 3 



sponge to climb upon. Since one specimen of this graptolite has 

 both sides preserved, it is referred on the basis of its habitus to 

 C haunogra'ptus. 



Descnption. — Ehabdosomes consisting of slender (0.12 mm. wide), 

 .straight stems (hydrocaulus 25 mm. long), which branch either very 

 infrequently or only near the base. Thecae short, conical, narrowing 

 distinctly toward base (projecting portion O.Y mm. long), alternating 

 on the hydrocaulus and projecting irregularly at various angles 

 langing from 90° to 20° ; though most often at right angles they are 

 at times sharply curved upward. Aperture circular, slightly ex- 

 panded. Periderm apparently smooth. Gonothecae not distin- 

 guished. 



Occurence. — ^Middle Cambrian, Burgess shale (Loc. 35K), Bur- 

 gess Pass, near Field, British Columbia. 



Holotype and faratypes. — U.S.N.M. No. 83484. 



Remarks. — This sj^ecies resembles C. novellus Hall, the genotype, 

 more than any of the other sf)ecies referred to the genus. (Ruede- 

 mann, 1908, p. 223.) Though ail the species are repent upon foreign 

 bodies, C. scandens seems not to have been so closely attached as the 

 others. 



In the description of the graptolite Ma-stigograptus (1908, p. 213) 

 I pointed out the fact that it was closer to the hydrozoans in the char- 

 acter of its thecae than any other form. Later (1919) Chapman 

 described two species {Archaeolafoea longicomis and Archaeocin/p- 

 tolaria skeatsi) from the Ordovician of Australia, which, on the 

 basis of the form of the hydrothecae and the discovery of the gono- 

 thecae attached to the hydrosome, in at least the first of the two, 

 he unhesitatingly referred to the hydroid coelenterates of the order 

 Calyptoblastea and the family Lafoeidae. He likewise placed Mas- 

 tigograp>tus Ruedemann in the same order and family, and pointed 

 out that Chaunograptiis also approaches his forms so closely that it 

 is referable to the same group. 



In the basal constriction of the thecae and the irregular angles of 

 divergence of the thecae from the hydrocaulus the new species of 

 Chaunograptus, even more than those previously described, sug- 

 gests relationship to the hydroids of the campanularid type. It 

 differs sharply in this respect from the true graptolites, the Den- 

 droidea and Graptoloidea, which according to evidence now accu- 

 mulating belong to an entirely different phylum. 



The fragments reproduced in Plate 2, Figures 4 and 5, indicate 

 the presence in the Burgess shale of a hydroid larger than Ghauno- 

 graptus scandens. The fossil is, however, too fragmentary to war- 

 rant a description. 



