170 SIXTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



In his Report on Wisconsin, Iowa and Minnesota, Dr. Owen has 

 described (on pp. 374 & 375) the Dikelocephalus miniscaensis and 

 D. granulosus. From specimens collected at the same localities, I 

 have recognized these species so distinctly as to leave no doubt 

 of their identity. While possessing some characters of glabella in 

 common with typical species of Dikelocephalus, there are other 

 features which appear to me quite incompatible with that genus. 

 The fixed cheeks are wider, and the facial suture has a different 

 direction, while the movable cheeks are equally distinctive in their 

 form and in their posterior extension. The surface-marking in both 

 species, but particularly in D. granulosus, is very peculiar, and 

 unlike anything known in typical species of Dikelocephalus. I 

 have found it necessary, therefore, to separate them from the 

 latter genus. At the same time there is equal difficulty in referring 

 them to any established genus, so far as I have access to published 

 scientific works. I therefore suggest a distinct generic term that 

 may include these two species, which, from present knowledge, I 

 regard as similar generic forms. 



GENUS PTYCHASPIS ( n. g.). 



[ Gr. Tzrvxri, plicatura; aaing, scutum.^ 



Head broad and strong, with wide depressed - convex cheeks. 

 Glabella cylindrical, convex, deeply lobed or transversely fur- 

 rowed, very prominent in front. Eyes anterior to the middle. 

 The facial suture cutting the anterior border at a point between 

 the eye and the glabella, or almost in front of the eye ; and 

 from below the eye it proceeds obliquely and in a slightly 

 curving line to the base, at a point near to, or a little Avithout 

 the centre of the cheek, leaving the movable cheek of nearly 

 the same dimensions as the fixed cheek. Movable cheek sub- 

 trapezoidal, with a strong thickened border, which is extended 

 into a spine. Eyes unknown. Palpebral lobe, in one species, small. 



The general direction of the facial suture is similar to that of 

 Arionellus ; but the eye is more anterior, though of the same 

 form. The strongly lobed cylindrical or subcylindrical glabella 

 is a very distinctive feature. Thorax with strong articulations, 

 the axis elevated, and the annulations marked by abroad node 

 at their extremities : ribs marked by a subcentral groove, and 

 angularly bent backwards near the middle. Pygidium somewhat 

 parabolic ; the axis strong and elevated, marked by several 

 annulations, and the lateral lobes by divided ribs. 



