I I: \< 1 1|. \ 



- nf tlic v.ihe-. Tin- ir-'iiii- l.iii-ii,-liiliHii alloid- 

 with a "frill." 



\- !_, ird- tin- ^rnlo^ic.il nr time di<tril>ution nf the ' ili.it 



the\ I'.. -in in the upper divi-ion- of tin n. if indeed they ai 



be reckoned a in mix the f, ,--il- known. In the Lower Silurian depo-it- ;ili . 



they iM-ciir in such great numl>er- and variety, tl. doubtful if tin ul.i 



tion-of the order at any -ul -.pient time exceeded them in ti The 



predominant t \ ; ,\ hile holdin;.' their own 



perhap- through the I'pper Siluria'i. were greatly reduced during |ie\miian an<l 

 'arliiiiiifi-riiu- i .'1 are now totally e\tr MM- ivcent f.nnilie- ami genera 



on the other haml were >|i.irin^l> .'iite.l. luit taken a> a whole the Silurian 



ii-ixla fauna i> 'li-ciilfilly |"'ciiliar.* 



Ill the I |>j>i>t Silurian foniiation^ the '//././ ami /"////.////-A/ -till |.relmu- 



inate.l. luit the fauna \\< \ tied, led accession- in the way of genera re-ai'li"l 



a- l-eloiitfiiitf to the family ' '///'//'//. The 1 > voinan i >-traco<la. though less nnnie: 



nt from the I |.j,er Silurian type.-, mo-t of the old gener 

 more or le sparingly repre-ente,|. Several ger /*. .lone-, ami 



'liilinn. 1'lricli) are so fa: It peculiar to t hi- system of r< 



The la fauna o: rous dep n the contrary, while retaining 



many -mall ,-pecies of essentially Silurian genera likt irirlriu ami 



I'n'miti'i. \vhi<-h occur a--ociate<l with the related genera Iifi/ri<-liielln ami Hei/rirhi- 

 opsis ami numeroii- forms of the pn y estahli-heti types of the Cyi>rid<i . 



nevertheless assumed a distim-tive aspect through the strong ilevjlopment of hitherto 

 unknown type- of I'yjirin /'/-/. 



In succeeding formation- the ,da are everywhere poorly represented in 



the Tria--ic ami .lura ic. Hut in the ' rata of Europe cer- 



tain L r ''iiera, Ci/then illy, tlevelop an astounding variety ami wealth of spc 1 ' 



The form- are all small, ami this may in part account for the fact that -o few i 

 been discovered in Am ages. 



The genera having, or he!;, 



in the variou- formation- a- I >li" . 1'hilm 



:feroii-: /' Silurian and ('arhoniferou-: Cijll 



Silurian, t 'arlioniferou- ami IVrmian- 



Silurian. l>e\onian. i arl,oniferoii- and I'ermian; fii/tli', , -iliirian. I". 



I'arlioniferou-: ' . Silurian ami | iurian: 



i'iil'1. ill ' '.ollifei. 



Th HUB plc.-d Inlo rrrnl f*t,. 



In my 



