CONTRIBUTIONS TO PALEONTOLOGY. 113 



mm 



The Trilobites enumerated and described in the preceding pages 

 include all those satisfactorily known to me at this date, from the 

 Upper Helderberg, Hamilton and Chemung groups, with the excep- 

 tion of the following species which was omitted in the proper place. 



HOMALONOTUS DEKAYI ( Green, sp.). 



Dipleura dekayi : Green, Monograph, p. 79. 



Niittainia sparsa : Eaton, Geological Textbook. 



Ho malonotus dekayi : Yanuxem, Report of the Third Geological District, p. 150. 



— — ; Hall, Report of the Fourth Geological District, p. 205. 



This species is known in the Hamilton group from near the Hudson river 

 to Lalse Erie ; but is comparatively rare on the west of Cayuga lake, and 

 extremely rare to the west of the Genesee valley. > 



The Phacojis nupera (^Calymene nupera, Report 4th Geol. District of 

 New- York), from the Chemung group, may probably be only a variety of 

 Phacops rana^ though its condition is such as not to admit of critical 

 comparisons. 



l^c 



I have had no opportunity for investigating the following species, de- 

 scribed by Mr. Conrad in the Annual Report on the Palaeontology of 

 New- York for 1841, p. 48, from the Schoharie grit and Onondaga limestone. 



" AsAPHUS? ACANTHOLEURUS. Pygidium very wide at base ; margin 

 " lunate, but projecting in the middle. A broad space between the ends 

 " of the ribs and the margin, on which are nine thick erect spines, the 

 " central one largest. Surface of the lobes with coarse tubercles. Loca- 

 " liti/ : Near Schoharie, in limestone with Odontocephalus (Onondaga 

 " limestone), found by Mr. Gerhard jr." 



*' A.? denticulatus. Pygidium with a lunate margin, denticulate at the 

 " termination of the ribs : ribs simple, with two rows of minute tu- 

 " bercles on each. Locality : Schoharie, in Grit N° 18. Found by Mr. 

 " Gebhard." 



A wax cast, from an impression of the first of these species, shows a 

 character of pygidium not unlike that of Dalmania myrmecophorus. Both 

 species doubtless belong to the Genus Dalmania. 



[Senate, No. 116.] 15 



