TKII.OBriF.S Ol' THE ChAZV LlMES'lONK. .341 



smooth, dejjressed border. 'I"he posterior end of one perfect pygidium 

 is prolonged into two short flat lobes.' Whether this is due to acci- 

 dental causes, a pathologic condition of the individual, or whether it 

 is the normal form, the material at hand is not sufficient to indicate. 

 Axis very narrow and convex, ending abruptly at the border. It 

 shows ten or twelve distinct annulations and sometimes more faint ones 

 can be made out. The pleura show about the same number of nar- 

 row, distinct ribs, which are very strongly outlined on the convex ])or- 

 tion of the pygidium, but become faint on the border. 



Surface minutely granulose. 



Afeasiireiiieiifs. — A cranidium : length 22.5 mm.; width at ends of 

 fixed cheeks 28 mm.; length glabella 16 mm. A small cranidium : 

 length 4 mm.; width at ends of fixed cheeks 3.5 mm. Glabella 3 

 mm. long. A large cranidium : length 100 mm.; width of front 130 

 mm.; length of glabella 68 mm. A large pygidium : length 78 mm., 

 width 58 mm.; axis 40 mm. long, 10 mm. wide at the front. 



This fine species should be compared very carefully with AsafJnis 

 tyranniis Murchison, as it agrees with it in many particulars of both 

 cephalon and pygidium. The glabella, glabellar furrows, shajte of 

 cranidium and presence of a glabellar spine are the same in both spe- 

 cies. Asapluis tyranmis is one of the typical Llandeilo species, and 

 does not seem to occur outside the typical region in South Wales. 



Locality. — Most of the specimens are from the trilobite layers on 

 the east side of Valcour Island, but one cranidium was found in the 

 reef at Smuggler's IJay, and another at McCullough's Sugar Bush, 

 Chazy, New York. The specimen figured on plate 10, figure 20, was 

 loaned by Erastus M. Hudson, who found it on the east side of 

 Valcour Island. 



Asaphus, species alpha, beta, and gamma. (Plate 1 2, figures 8-10. ) 



On jilate 12, figures 8-10, are shown the pygidia of three species of 

 trilobites, all of which are very small, mostly less than an eighth of an 

 inch long. Although they cannot now be assigned to any of the species 

 here described, they may be the young of some of them. It is an in- 

 teresting fact that, although species aiplta and beta occur abundantly 



' These lobes have been represented on plate 10 as more pointed than the speci- 

 men shows them. Two more specimens worked out recently show this same condi- 

 tion, and the outline of the lobes is more nearly as in the reconstructed figure on 

 plate II. 



