TKII.MMTB8. ' ' :; 



I 



truo Lichns. A diflicult y, more apparent than real, in assigning the species of 

 lii-lmds to their natural ^n>u|m, arises from the frequent recurrence of extravagant 

 -i > lis of ornumentution in tfnmp- II.IMHJJ a totally different character of cephalic 

 loli.uion. Tlui> in Mi-infii.is, rinliftndopus and lloplolichaft may occur along, club-like 

 extension of th> frontal lobe; riatytnetopux and Conolirhas may both have subconical 

 frontal lobes, concave on their posterior slope; I'latymeiopus and Ifoplolichas may 

 ha\c tln> frontal lobe garnished with erect tubercle-spines. These are instances of 

 inoi pine ri|uivalence in diverse groups, which cannot be accorded a high ttignificance 

 in the association <>f the species. 



\\ ni.u Miggeat the following subgeneric division of the North American 

 species of Licha*: 



AKOKII. Goldfuss -Mulillf glabellar furrows obsolete, posterior furrows mure or low Indistinct; 



<>ut>T lateral margins of glabellar lobes convex; third lobes obsolete. Pygldlum with 23 



arm illation son the axis, mad narrow, round spine* on the margin. A longitudinal ridge extend* 



f ruin Hi'- , \; ri-iniiy of the axis to the margin. Elerated portions of the body often echlnaU*. 



A . ifftfnt>frgennt Schmidt, var. paulianta Clarke. Galena. 



pUfeUnoidn Green. Nlaicara. 

 A. cotuamguinfiu Clarke. I. A 1 1- Nlcrherg. 

 A. eontufnt Hall. U|ip>-r II>-lderberg. 

 /-. (Conotiehat) hltpidut Hall. Upper Helderberg. 

 /.. (ConoliclHu) eriopit Hall. Upper HelderberK- 



The last twu seem to be more at home here than In lhi> aubgenuK Vonolirha*, on account of subtan- 

 tlal difference* from the latter In glabellar lobatlon and form of the pygldlutn.. 



PLATYKOTUS, Conrad. Glabella depressed; middle furrows obsolete; frontal lobe depressed at Its 

 narrowest point; third lobes obscure, but present. I'ygldlum with three pairs of broad, acute, 

 flat spines; axis short with 12 annulatlons. 

 /. harriti Miller. Hudson River. 

 /-. Mtoni Blgsby. Niagara. 

 tL. nrrfiu Hall. Niagara. 

 L. brtvicep* Hall. Niagara. 



PLATYMETOPUS, (Angelln) Schmidt. Lateral glabellar furrows open directly Into the occipital 

 furrow: no third loben; all loben depressed-convex, all furrows narrow; dorsal furrows con- 

 cave inward. 1'ygidluui with two pairs of lateral spines and a bluntly blsplnou* caudal 

 termination. 



L juketi Billings. Quebec. 



L. mittganrntu Hillings. Chazy. 



L. trrntiinfruif Hall. Trenton. 



L. eufullut Meek and Worthcn. Trenton, Galena. 



/~ roMiiMi Ulrlch. Galena. 



/- bieomii Ulrlch. Galena. 



Hall and Clarke. Frontal lobe elevated, lateral lubes large and highly convex, 

 all spinif-T..-.-: third lobes absent. Occipital ring broad, with double axial spine. Dorsal 



furrows^ -in. ir n<le very small. Border broad. 



C. draeon Hall. Upper IIi-lil<>rl*erg. 

 C. grjfpt Hall. I li-rlierg. 



TKRATASPIS, Hal!. Fnintal lobe ovoid, constrictnd Iwlow; dorsal and lateral furrows very broad; 

 lateral lobes not sharply <letln--i. highly elevated, direct* <rly. splnous. Occipital nnj; 



very broad centrally, with baculate processes. I'ygl'limn with four pairs of long, splnlferoos 

 caudal processes. 

 T. grtiniti* Hall. Upper H.'l.l. r)erg- 



