24 bulletin: museum of comparative zoology. 



glabella tapers into a spine, this feature not being correctly shown by 

 Weller's figures. I had at first believed that this specimen repre- 

 sented a distinct species, but fortunately was able to see the type in 

 Mr. Teller's collection. That the species belongs to Trochurus in- 

 stead of Dicranopeltis is shown by the dorsal furrows, which curve 

 inward instead of outward, at the posterior ends. 



Formation and locality: — The specimen is from the Niagaran at 

 Wauwatosa, Wisconsin. 



ODONTOPLEURIDAE Burmeister. 



Ceratocephala goniata Warder. 



Plate 3, fig. 3-5. 



Ceratocephala goniata Warder, Amer. journ. sci., 1838, ser. 1, 34, p. 378, fig. 

 Clarke, 44th Rept. N. Y. state mus. nat. hist., 1892, p. 91-100, pi. 1, 

 f. 1. Kindle, 2Sth Ann. rept Dept. geol. and nat. res. Indiana, 1904, 

 p. 480, pi. 24, f. 13. Weller, Bull. Chicago acad. sci., 1907, no. 4, pt. 2, 

 p. 255, pi. 23, f. 1-2. Raymond, Bull. Victoria mem. mus., 1913, 1, p. 38. 



Acidaspis danai HaU, Geol. surv. Wise, 1862, 1, p. 432 (no description); 18th. 

 Rept. N. Y. state cab. nat. hist., 1865, p. 28, adv. sheets; 20th Rept. N. Y., 

 state cab. nat. hist., 1868, p. 333, pi. 21, f. 8-9; 1870, rev. ed., p. 423, 

 pi. 21, f. 8, 9. 



Acidaspis ida WincheU and Marcy, Mem. Boston soc. nat. hist., 1865, 1, p. 

 106, pi. 3, f. 13. 



The cephalon of this species is, thanks to Professor Weller, now well 

 known, but hitherto the thorax and pygidium have not been noticed. 

 The Day collection in the M. C. Z. contains parts of two pygidia and 

 a fragment showing a portion of five segments of the thorax. The 

 pygidium is like that of Acidaspis portlocki Barrande, with a large 

 median spine, on each side of which are two smaller spines, then a 

 large spine, and finally an outer small spine. Each spine gives off 

 small thorns on each side. The thorax is similar to that of C. verneuili 

 Barrande. However, as only the central portion has been seen this 

 part of the body would not be expected to show specific characteristics. 

 The cephalon seems to be more nearly allied to C. vesiculosa than to C. 

 verneuili, and a cephalon in the M. C. Z. gives indication that marginal 

 spines were present on the free cheeks. The pygidium found with the 

 cranidia at Wauwatosa are unlike those ascribed to C. vesiculosa by 



