360 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



DOLICHOMETOPUS ACADICUS Matthew 

 Plate 53, figs. I, la-c 



Dolichometopus acadicus Matthew, 1897, Trans. Royal Soc. Canada, 2d ser., 



Vol. 3, Sec. 4, p. 185, pi. 3, figs. 6a-d. (Described and figured as a new 



species.) 

 Dolichometopus acadicus Matthew, Lorenz, 1906, Zeits. deuts. geol. Gesells., 



Vol. 58, Pt. 2, p. 75. (Compares D. acadicus with his Bathyuriscus 



asiaticus.) 



Original description. — " Body covered with a very smooth test. 



" Head-shield margined all round and having an intramarginal 

 furrow. Eyes large, furnished with a semicircular orbital lobe. The 

 facial suture curves backward and downward behind the eyes, and 

 has a direct extension forward before the eyes. Glabella distinctly 

 outlined, bent downward in front, subclavate, without furrows, 

 rather squarish in front, extending to the anterior marginal fold, 

 about twice as long as the width at the base. Occipital ring lenticular 

 in outline, divided from the glabella by a shallow furrow. Fixed 

 cheeks narrow, width about half of that of the glabella at the base. 

 Posterior angles of the middle piece produced backward and bent 

 downward. The eye lobes are as long as the width of the glabella in 

 front 



" A pygidium, which also occurs with the above heads and cheeks, 

 is not unlike that of an Anomocare, but differs in having a blunter 

 and stouter rachis than is usual with pygidia of this genus ; we 

 regard it as probably the pygidium of the Dolichometopus. It has 

 a rather narrow prominent rachis, having four faintly marked rings, 

 besides the more distinct half-ring in front ; the side lobes have three 

 faintly marked ribs, besides that at the front margin ; the lateral mar- 

 gins are flattened and without a fold. 



Sculpture. — " This consists of a minute granulation, made visible 

 only with a lens. 



Size. — "Length of the head-shield, ii mm.; width of the middle 

 piece of the head, lo mm. Length of the movable cheek, lo mm. ; 

 width, 5 mm. Length of pygidium, 6 mm.; width, lo mm 



" This species differs from the Swedish form {Dolichometopus 

 sueclcus) by Angelin,' in having a more direct suture before and 

 behind the eye, and a longer eye lobe. It differs from the same species 

 as figured by Brogger " in the course of the dorsal suture, and in the 

 less numerous joints in the rachis of the pygidium." 



^ Pal. Scand., pi. 37, figs. 9, gb-c. 



" Om Paradox, skifrene v. Krekling, Nyf Mag. for Naturvidensk., 1879, pl- 3, 

 figs. 12, 12a. 



