78 North American 



its extremity to the interior of the little funnel-shaped lorojection 

 formed upon the under side of the head-shield. These details 

 are very distinct, owing to the very perfect preservation of this 

 specimen Avith its shell. After this we cannot accept any other 

 interpretation for the genus Cheirurus than that which we have 

 given." 



Valerian von Moller, in his article on the Trilobites of the 

 Carbonifei-ous formation of the Urals, in 1867,. p. 44, notices 

 these auxiliary impressions on the head of Pliillipsia EichimilcU, 

 "as very distinct deep funnel-shaped openings which run a little 

 obliquely and enter into the under side of the cephalothorax.'' 

 He cites the opinion of McCoy and of Barrande, and remarks, 

 "I quite agree Avith the observations of Barrande, and. I feel 

 sure the more one examines these indentations the more one 

 feels satisfied that they are only superficial openings." 



Dr. Henry Woodward, in his Monograj)h of the British Car- 

 boniferous Trilobites (Palseont. Soc. Lond., 1884, p. 71), gives a 

 general review of the literature on this subject and remarks : — 

 '• These puncta may be. like the fenestrcB in the head of Blatta 

 urientalis, either rudimentary ocelli or the seat of some other 

 nerve-sense, and may have been, as in Blatta and in Serolis, co- 

 vered with a thin transparent portion of the integument, which 

 served either as a simple eye, a tympanum, or an olfactory jiore. 

 AVe have referred to these fe?iestr(B in the head of Blatta because 

 they are placed, like those of the trilobites, on a suture of the 

 head, and in front of the compound eye." 



The interpretation of these cone-like organs observed upon 

 Froetus Missouriensis seems to favor the conclusion of Dr. 

 Woodward, that is, that they were organs of hearing. 



PKOETUS LOGANENSIS, Hall & Wliitfield. 



Proetus Lognnensis, Hall and Whitfield, 18T7, U. S. Geol. Expl. 40th Par., 

 Vol. IV, p. 264, pi. 4, fig. 33. 



The pygidium of a small species differing very materially from Proetus 

 peroccidens occurs at Logan Caiion. ' ' The form is more nearly semicircular, 

 being but very slightly paraboloid. The axial lobe is highly convex, ra- 

 pidly tapering below and terminating abruptly a little within the posterior 

 margin ; anterior end forming fully \ of the entire width of the shield. 



