66 NEW YORK STATE MUSEUM 



DESCRIPTIONS OF SPECIES 



TRILOBITES 

 Dalmanites pleuroptyx Green 



Plate 12, figures 2-4 

 For references see Palaeontology of New York. 1888. 7:28 



This characteristic species of the New Scotland limestone has not 

 been seen in any other of the areas here discussed, its place apparently 

 being taken by D. micrurtis Green, a closely allied species whose 

 differences from the former have been elsewhere indicated [see reference 

 above]. We have here a fairly well preserved cephalon with the gently 

 crenulated anterior margin of D. pleuroptyx though with somewhat 

 longer head and not clearly denned anastomosing sulci on the free cheeks, 

 in these respects like D. dolbeli of the Grande Greve limestone. 

 There are present also pygidia which correspond quite fully with the typical 

 form of the species, bearing 10 to 11 lateral sulcate ribs, 12 to 14 axial 

 annulations and a short blunt caudal spine. 



Localities. Telos lake, i mile above Blind Cove point ; loose at Cun- 

 ningham's camp, 4 miles southwest of Matagamon lake ; Moosehead lake, 

 at Baker Brook point, and on the Folsom farm about 7 miles north of 

 Kineo ; Parlin Pond, north of Bean Brook on the Canada road. 



Dalmanites ploratus Clarke 



Plate u, figure 5 



Dalmanites ploratus Clarke. N. Y. State Mus. l.ul. 107. 1907. p.i6i 



There is a group of tuberculated dalmanites in the early Devonic 

 rocks, embracing D. dentatus Barrett (which the ornament of the 

 cephalon shows to be a Corycephalus), from the Port Jervis Oriskany, 

 the allied D. bisignatus Clarke and D. phacoptyx H. & C. 

 from the Becraft Mountain Oriskany. Of the last two the pygidium of the 

 former is a shield of slender proportions with regularly spaced tubercles 

 on the axis, in the other it is large and has coarse irregularly scattered 

 tubercles. The pygidium before us is of the general type of D . bisig- 

 natus but is larger and considerably more segmented. Thus D. bisig- 

 natus has 7 to 8 pleural ribs while D. ploratus has 15 to 16, the 

 former 10 to 12 axial rings, the latter 20 to 22. Notwithstanding this dif- 

 ference there is a similarity in the size and arrangement of the tubercles or 

 granules ; on the annulations there is a single row of four of which the 

 middle ones are largest. Passing to the apex of the spindle this middle 

 pair becomes more conspicuous by the disappearance of the others and thus 

 there appears to be a double axial row of these pustules. On the pleurae 

 they are scattered irregularly and faintly over the sulcate ribs. Our 



