NO. 24 PTARMIGANIA STRATA RESSKR 3 1 



PTARMIGANIDAE, new family 

 DOLICHOMETOPSIS Poulsen, 1927 



Poulsen described Dolichometopsis from cranidia, referring a 

 single fragmentary pygidium to the type species. This pygidium, how- 

 ever, is doubtful, what there is of it pointing rather to Kochiella. 

 Nearly complete specimens in the Ptarmigania fauna makes it prac- 

 tically certain that the pygidium of Dolichometopsis has a spinose 

 margin, four spines to the side. These spines, which increase in size 

 from front to back, may be longer than the pygidium or may be short 

 and sharp-pointed. In no case have they been eliminated. The most 

 characteristic feature of the pygidium, aside from the marginal spines, 

 is the heavy spine on the first axial ring. The thorax seems to have 

 seven segments. 



Poulsen recognized the relationship of Dolichometopsis to Albcr- 

 tella. Its nearest relative clearly is Ptarmigania. In fact, it is not 

 certain that the cranidia of the two genera can be separated in every 

 case when the pygidium is lacking. In this paper arbitrary separa- 

 tions were necessary in several instances. On the whole Ptarmigania 

 is more' granulose than Dolichometopsis, but one cannot be sure that 

 this criterion will hold at other localities for both have a granulated test. 



DOLICHOMETOPSIS LEPIDA, n. sp. 



Plate 3, figs. 31-33 



This species is represented only by cranidia and a libragene. It is 

 characterized by a long glabella, which expands slightly forward of 

 the eyes. The usual four pairs of glabellar furrows are visible, and 

 the occipital ring extends into a long stout spine. The fixigenes are 

 confined to the palpebral lobes, which extend forward to the third 

 pair of glabellar furrows and back to the occipital furrow. At the 

 widest point they are just exactly half the width of the glabella and 

 the eyes are moderately bowed with a nearby even curvature. As 

 usual the rear end of the eye lobe overhangs the occipital furrow. The 

 surface is granulose, the granules being rather numerous and evenly 

 distributed. Anterior to the eyes the fixigenes form a flange about 

 equal in width to the narrow concave brim, the latter being thickened 

 and heavily striated on the elevated edge. 



D. lepida has the longest glabella of the smaller forms. 



Locality 54s: 



Holotype and paratype. — U.S.N.M. Nos. 98501a, b. 

 3 



