32 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 76 



of the glabella, a small occipital spine, lineate surface markings, the 

 antero-lateral parts of the fixed cheeks subangular and their convex 

 areas pinched into a curved ridge. However, the glabella is not so 

 convex as in our species and relatively not so broad. Besides, the 

 pits on either slope are shallower, not so widely separated, and 

 extended both forward and backward into characteristic long shallow 

 sigmoidally curved furrows that are wanting in the American species. 

 In the latter, on the contrary, the posterior glabellar lobes are out- 

 lined in a manner wholly lacking in Hadding's figures of T. mohergi. 

 Then, taken as a whole, the length of the cranidium in T. hipunctatus 

 is decidedly less than in its Swedish ally, the anterior spines are 

 farther apart and distinctly separated from the adjacent slightly 

 produced angles of the frontal rim, the anastomosing surface ribbing 

 extends over the anterior halves of the fixed cheeks and the anterior 

 as well as the posterior parts of the glabella, and the fixed cheeks, 

 including the palpebral bands, are wider in front and more distinctly 

 triangular in outline. 



Compared with American species there are at least four that must 

 be counted as closely related to T. hipunctatus. These allies include 

 T. imypiMhctatus, T. prattensis, T. telUcoeiisis, and T. hircintts. The 

 distinctive features of each are given under their respective headings. 



The pygidium that is referred to this species is small, triangular 

 in outline, very convex, with very narrow concave pleural lobes and 

 correspondingly large axis. The first ring of the latter carries two 

 small spines near the middle, the second apparently a single though 

 probably a double headed larger node, the third, or terminal ring, 

 which is small and not deeply separated from the second, has a node 

 on each end. 



The free cheeks so far discovered with cranidia of this species are 

 all more or less imperfect. The rim is narrow even at the base of 

 the genal spine, of which usually only the stump remains. How- 

 ever, it is retained on the specimen from Lexington, Va., and its 

 strongly curved character, length, and weak base together probably 

 explain its loss in the other specimens. The ej^es are large but not 

 so bulbous as in the associated T. pustidatits, and the ocular facettes 

 are rather small but not minute as in T. rmfsticensis. They are larger 

 also than in T. pustnlatus. 



OccuTrence. — Over 50 specimens of the cranidium of this species 

 were collected from the Whitesburg limestone — a 20 to 40-foot zone of 

 dark gray, irregularly bedded subcrystalline limestone between the 

 Holston marble and Liberty Hall limestone — at Lexington, Va. Only 

 a single pygidium and only one free cheek were observed at this 

 locality. Cranidia occur equally abundant in the corresponding 

 limestone at localities in the vicinity of Albany, Tenn. At these 



