TU II." I: I TBS. 747 



IMlrmri..pu rwbbln.l 1 



peculiar Mil-conical protuberance. It is mainly in the latter feature that the species, 

 If a- it- pirts arc known. dihVrs from the Lidins trtntonensis Conrad. A well 

 preserved glabella of /'. cnrulln* occurs among the material from the Galena lime- 

 stone of Wykotl. Minnesota, loaned by I>r. Kobbiiis, and a fragment which may 

 represent the same species comes from the Trenton beds at Janesville, Wi>con>in 

 (MiiMMim No. M1J) 



l'i. \TV.M: I:<IHHIX-I I'lrii-h. (*p.). 1892. 



Lirh.u i //.././../I.-/MM / nWJ.mjii I 1.1:11 ii, 1902. Two n.-w Lnwi-r Silurian HpcclM of Llcbax ( 

 HoptollCfa 1-1. AIIKT. (Jeolnuisl, vol. \, No. 5, p. 271, UK*. la I'. 



The original an. I. as fur as I am aware, the only observed specimen of this 

 species, is a cranidium lacking only the anterior portion of the glabella, The species 

 i- .in interesting addition to the American lichads and presents some especially 

 noteworthy features. Among these is the stout baculiform anterior extension of the 

 frontal lobe of the glabella, which appears to be homologous with the produced 

 lobe of the well known lower Silurian species, L. rdorrhin Angelin* and L. pach;/- 

 ri/nrha li.ilnian. var. lo> '/ Schmidt,! rather than with such spinous processes 



a> tlinx- po^c-M'd hy L. Inrornis IMrich. Hnjtlnlirli,^ Iriru^iidnla Beyrich and //. 

 probosciil"! I 'ames. 



The character of the glabellar furrows, also, is of importance. These are very 

 narrow and sharply impressed, have the usual degree of curvature anteriorly, but 

 posteriorly become quite parallel and straight, debouching in the equally narrow 

 occipital furrow at right angles. Thus, as in so many of the American Silurian 

 species of Lichas, these grooves represent the continuous anterior and posterior 

 furrows, the median pair being lost by the coalescence of the first and second lobes. 

 The third pair of lobes we regard as obsolete. 



Fig*. 08, 40. The crmnUlium of I'latymetopiu robbinti Ulrich: with outUm* 



Elsewhere we have expressed the conviction that the lobation of the glabHla 

 must be given fir>t importance in the sub.Hvision of the genus /,/>/,</>. an-1 the nature 

 of this lobation with the total loss of the third lobes places thi- -p-.-ies with the 



PaUnntolacia r*adlnvl<-a. pt- I. p. . pi. xxxv; *f*. tn-e. MM. 



d.0.tbU. Sllor Tr > l.-n. pi I M IJ. IKM. 



