60 



BULLETIN 65, UNITED STATES ' NATIONAL MUSEUM. 



compression has so fallen as to extend nearly in the form of a circle. Though 

 it resembles somewhat CaJlograptus niaguroisis, yet the numerous rudimentary 

 branchlets and spinelike lu'ocesses distinguish it from that species. 



FonmilUni and Ideality. — This species is found in the "chert-beds" of the 

 Niagara formation at Hamilton, Ontario. The best specirueu was obtained from 

 Mr. Edward McLaughlin, of Hamilton. 



Gurley's notes on this species follow : 



To this species I have referred, in all, sixteen specimens, several of the more 

 fragmentary ones with some doubt. One specimen (PI. 4, fig. .5. text fig. S2) 



shows the base, and may be described as 

 follows : 



Polypary (in this specimen) semicircnlar- 

 flabelliform, originating in, and sessile 

 upon, a transversely extended, apparently 

 thick, fibrous, or discoid base of a black 

 carbonaceous texture. From the base arise 

 about three main branches, which bifur- 

 cate and rebifurcate in their course toward 

 the periphery, the resulting somewhat 

 wavy branches running nearly straight out 

 to the periphery, where they seem to termi- 

 nate in two or several twigs or spikelets. 

 Along their course their sides are beset 

 with " rudimentai-y branchlets," etc., 

 whose length may reach 1 mm. In this 

 species, however, these lateral fringing 

 l)rocesses are fine, giving the branches a 

 feathered appearance. They ue\er reach the thickness and remoteness of those 

 .=een in A. walken. The usual width of the branches is 0.4 mm., but some reach 

 0.5 mm. About 40 branches occur in 25 mm. of width, the intorsiiaces thus 

 being quite narrow. Only two 

 theciB are visible. These are 

 0.4 mm. apart (corresponding to 

 about 60 in 25 mm.). Indica- 

 tions of dissepiments are not 

 wanting (some structures very 

 much like them are visible), and 

 although not entirely willing on 

 strength of the present material, 

 I may say that I incline very 

 strongly to doubt their asserted 

 absence in any of these genera, 



and also that in my opinion there is hardly a more dubious character than 

 " absence of dissepiments." For the assertion of such a condition the material 

 must be absolutely irreproachable, as of all the structures in the polypary the 

 dissepiments, being the most delicate, are the first to disappear. 



There can, I think, be no doubt that the present form is Spencer's species. 

 Both as a diagnosis by exclusion, and by its general agreement with his descrip- 

 tion and figure, its identity is satisfactorily made out. 



Horizon and locality. — Niagara chert and glaciated chert, Hamil- 

 ton, Ontario. ^ 



Plesiott/pes.— Cat No. 55307, U.S.N.M. 



Fig. 81. — .\cantuuguaptus ptjlcher 

 SrENCKR. Copt of Spencer's fig- 

 ure. 



Figs. 82, 83. — Ac.\xTHOGR.irTUS pulcher Spencer. 

 82, Specimen preserving base. (See also Pl. 

 4, fig. 5) ; 83, Less complete khabdosome. 



