COCCOSTElB-E. 
283 
1844. Coccosteus cuspidatus, L. Agassiz, ibid. pp. 28, 137, pi. xxxi. 
fig. 4. [Median dorsal plate ; Edinburgh Museum.] 
1848. Coccosteus microspondylus, F. M‘Coy, Ann. Mag. Nat. Hist. [2] 
vol. ii. p. 293. [Imperfect skeleton ; Woodwardian Museum.] 
1848. Coccosteus pusillus , F. M'Coy, ibid. p. 298. [Ditto.] 
1848. Coccosteus ? trigonaspis , F. M‘Coy, ibid. p. 299. [Ditto.] 
1855. Coccosteus lotus, F. M‘Coy, Brit. Palseoz. Foss. p. 002. 
1855. Coccosteus oblongus, F. M‘Coy, ibid. p. 603. 
1855. Coccosteus microspondylus, F. M‘Coy, ibid. p. 602, pi. ii. C. fig. 4. 
1855. Coccosteus pusillus, F. M f Coy, ibid. p. 603, pi. ii. c. fig. 5. 
1855. Coccosteus P trigonaspis, F, M‘Coy, ibid. p. 603, pi. ii. c. fig. 6. 
1860. Coccosteus decipiens, Sir P. Egerton, Quart. Journ. Geol. Soc. 
yol. xvi. p. 128. 
1860. Coccosteus milleri, Sir P. Egerton, ibid. p. 135, woodc. figs. 5, 6, 
[Edinburgh Museum.] 
1875. Coccosteus decipiens, W. H. Baily, Figs. Charact. Brit. Foss, 
pi. xxxiii. fig. 3. 
1880. Brachydeirus milleri, A. yon Koenen, Zeitschr. deutsch. geol. 
Ges. yol. xxxii. p. 675. 
1883. Brachydeirus milleri, A. yon Koenen, Abk. phys. 01. k. Ges. 
W iss. Gottingen, vol. xxx. p. 20. 
1883. Brachydeirus pusillus, A. von Koenen, ibid. p. 20. 
1888. Coccosteus decipiens, I!. H. Traquair, Geol. Mag. [3] vol. v, 
p. 511. 
1889. Coccosteus decipiens , B,. II. Traquair, ibid. vol. vi. p. 4, pi. i, fig. 2. 
Type . Imperfect skeleton^’; British Museum. 
The type species, attaining a maximum length of about 0*4. 
Cranial shield hexagonal in form, the outer lateral angles acute, 
and the breadth between the latter considerably greater than the 
total length ; median occipital much broader than long, abruptly 
truncated in front, its anterior end being only half as broad as the 
posterior ; the anterior two-thirds of the shield gradually arched 
from side to side, flattened or depressed above, and the posterior 
portion of the median occipital plate rising to a sharply bent longi¬ 
tudinal ridge, corresponding to the laterally-arched contour of the 
median dorsal plate of the trunk immediately behind. Median 
dorsal plate as long as the cranial shield, and twice as long as 
broad, much arched from side to side, gradually tapering in its 
posterior half and produced into a long, blunt point; anterior 
border slightly excavated. Anterior ventro-lateral plates not much 
longer than broad, shorter than the posterior ventro-laterals, which 
are twice as long as broad and produced at each postero-lateral 
angle into a short spine; exposed portion of both median ventral 
plates longer than broad, the lateral angulation of the posterior 
median being almost at its middle point. Tuberculations of mode¬ 
rate size, never confluent, and rarely, except in the lateral plates. 
