HYDROZOA--GRAPTOLITOIDEA 



1 1 



vehicle, i>r a filiform pn>\ iinal virpila, or au r ain into two ipimform r B 



proer^es. Sdinrt inirs tin- hv< lr >< iina remains undh idcd, somet inn-s it forms 

 branches which may diverge at \arioii> aii^'lrs ; in other cases two or four 



)iiono]!-ioni(iiaii polyparies may be placed ia<-k to back with their dor.-al walls 



enali-seiiii,'. thus :, r i\in^ rise to di ..r tetra prionidian colonie-. In tin- latter 

 types the i-iM-iiitsark i- (oniiiK.nly divided ly one or two median septa, and 

 the primordial luids originate at \ariniis distances along the simlar margin. 



( )eea>ional sjteeimens of di|>rioiiidian ( Jrapt "lit es ha\f 1 n found lirarin^ 



lai'-e -a. like in- irregularly expanded eorneoiix >t nu-tuivs ( Ki^'. -""'). whieh an- 

 ei.mpai'al.le \\ith the nvai-ian eapsnles (*/'*//////////) of recent Sei'inlarians. Furthrf- 

 moi-e, the singular Ixxlics kimwn as lhui:<niii,i -small, oval, lell -shaped. tr 

 d.nical chitinoiis ca])sules, which are often a-suciated with ( Iraptnlitrs in vast 

 nmnliers are re^ardi-d \\\- Nicholson as detached ^raptolitic ^onan^ia. 



(Iraptolites coinmoiilv occur in argillaceous schists, more rarely in limestone 



formations, of the Upper ('ainlrian, ( )rdm ician, and Silurian system^. They 



si-mi to have swarmed in the mnddiei' portions of the sea, and floated either as 



\immin^ colonies, or, in ram- instances, remained stationary u'ith the 



'siciila embedded in the mud. They are divided into three groups: Mn>- 



jir/t, ;,/</,', /iifii-i'niiit't', and JM in/if i,ltn: 



Sub Order A. MONOPEIONIDAE. Hopkinson. 



uni*-ri"l/f/ i/cri'/ujin/ <>n //// x/Wr nf jiii/i/jinn/ //////// o 



t 



(lein. 

 Ia-kf! J02, 206). 



I5arr. ; /'^///"A^//-"/////x and 

 Hydrosoma undivided, rectilinear, or curved, some- 



lurin(Alnm8 



(IrafiMiu 

 (ii-riiiuny; '', M 



- lnrian 



Klintsli.-l.l. Si-i.tlaii.l. Shf.w- 

 in- sicula (aft.T I.-tp \\nrtli); 



tiii-rii-ulntu*. 



U-HT. Silurian: I'l-.i-uiMatt. r 

 I5;uiaiilc). All ti^'Urrs natural 



vii-ian ; I'e.inl l.-vi-, Canada (after 

 Hall). 



JOT. 



Silurian ; Xi-kk.)\vit/, 

 "r Harramlf). 



in-ar 



fta. 



l>iiliiniiHiri>t'<!> 

 <r.luviriaii ; 

 (afti-r Hall). 



|.,-\ i 



a, Hall. 

 Canada 



Hall. 

 1'uint I 



times helicoid. Hydrothecae in contact, usually overlapping. Aperture either 



entire or contracted, often directed downwards. Almmlant from base to 

 summit of Silurian. 



