ART. 21 ORDOVICIAN TRILOBITES ULRICH 41 



which do not connect with the dorsal furrows. The nuelial ring is wide, and 

 bears a long slender median spine. The specimen is a cast of the exterior, and 

 shows a very fine granular ornamentation on the palpebral lobes. 



Measurements. — The cranidium is 4.00 mm. long and 5.00 mm. wide across 

 the palpebral lobes near the front. The glabella is 2.25 mm. long, and 3.00 mm. 

 wide at the base. The nuchal spine is about 1.25 mm. long. 



This species appears to be most closely allied to Telephus mobergi Hadding 

 (Geol. foren. Forhandl., 1913, 35, p. 37, pi. 2, fig. 12-17), agreeing with that 

 species in the possession of one pair of glabellar furrows, which, however, are 

 differently placed, and in having ornamentation only on the palpebral lobes. 



T. troedssoni differs from T. mnericanus Billings in that the glabella tapers 

 more rapidly forward, and in possessing a nuchal spine. 



Horizon and Locality. — A single cranidium was found by the writer in 

 Athens shale associated with Nemograptus gracilis in a cutting on the railroad 

 2 miles northeast of Athens, Tenn. Named for Dr. Gustav Troedsson who 

 was with me when the species was found. Holotype (M. C. Z. 1,723). 



Study of Raymond's poorly presefved holotype of this species and 

 of the clay mold of it that is illustrated in Plate 5, Figure 17, sug- 

 gests that it is really a closer ally of Hadding's T. niohergi than is 

 indicated by the above quoted description. The exterior ornamenta- 

 tion of the fixed cheeks, or palpebral lobes as Raymond calls them, 

 is nearly obliterated, but its remains leave little doubt in my mind 

 that it was not of the granular kind but rather of the reticulated type 

 that occurs in T. tnobergi and is perhaps best developed in such 

 American species as T. hipunctatus and T. prattensis. Certain ob- 

 scure thin longitudinal ridges on the posterior half of the glabella 

 also suggest remains of the kind of ridging of the corresponding 

 parts of the exterior surface of the head that prevails in the men- 

 tioned Swedish and American species. Neither the reticulation of the 

 cheeks nor the longitudinal ridges of the glabella seem ever to show 

 on clean casts of the interior. 



A few more or less distorted specimens, comprising a couple of 

 •oranidia, a free cheek, and a pygidium from basal Athens near Long- 

 view, Ala., that prior to seeing the type of T. troedssoni I had re- 

 ferred with question to T. niohergi^ may very well be conspecific 

 with Raymond's species. There are some differences when we com- 

 pare these Alabama specimens with the illustrations of the mentioned 

 Swedish species on the one hand and with the type of T . troedssoni 

 on the other. But since the latter species has been established and 

 though closely related to is yet distinguishable from T. mohergi^ and 

 as I find it easier to explain the observed accidental differences from 

 the type of T. troedssoni than I can account for the differences noted 

 in comparing the Alabama specimen with the Swedish species, it 

 seems best for the present to refer them to Raymond's species. 



A few statements regarding each of the Alabama specimens here 

 under consideration and illustrated on Plate 5 may be desirable. 



