34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



NEOLENUS INTERMEDIUS, new species 



Plate 6, Figures 1-7 



This species, as its name implies, is an intermediate form between 

 N. superbus and A^ iniiatus. It differs from both of those species in 

 the absence of an occipital spine; and in having the sides of the 

 glabella more nearly parallel and with the glabella less expanded in 

 front, and somewhat more pointed or less abruptly rounded. The 

 pleural lobes of the thorax have a terminal spine on the pleurae ex- 

 tending backward somewhat more abruptly than in either of the 

 other species. 



The pygidium has five or six rings in the axial lobe and a terminal 

 segment. A'', iniiatus has ten or eleven rings in the axial lobe and 

 N. superbus has eight rings; N. intermedins has the same number 

 of terminal spines as N. superbus, but the spines are curved back- 

 ward much more than in the latter species. 



As far as known, this species does not attain the size of either 

 N. superbus or N. iniiatus. The largest cephalon in the collection 

 has a length of 35 mm. The proportions of the head and pygidium 

 are about the same as A^ superbus. The hypostoma referred to this 

 species is proportionally broader and with a larger body propor- 

 tionally than that of A", iniiatus or A'', superbus. In other respects 

 it is very much like the hypostoma of N. -superbus. 



Dimensions. — A dorsal shield 74 mm. in length has the following 

 dimensions : 



Cephalon : mm. 



Length 26. 5 



Length of glabella 21.0 



Length of QYQ lobe 4.4 



Width at posterior margin 44.0 



Width of glabella at posterior margin 13.5 



Width of glabella at anterior end 15.0 



Thorax : 



Length 27 . 



Width 41.0 



Width of axial lobe at first segment 13.0 



Width of pleural lobe at first segment 13.5 



Pygidium : 



Length 20. 5 



Width 35 . o 



Width of axial lobe at anterior ring 10. o 



Width of axial lobe at posterior ring 7.5 



