294 
AETHRODIRA. 
Dermal plates of Placoderms, too imperfect for satisfactory deter¬ 
mination, have also been assigned to Coccosteus under the following 
names 
Coccosteus agassizi , J. Barrande, Syst. Silur. Boheme, vol. i. suppl. 
(1872), p. 638, pi. xxix. tigs. 3, 4, 6-8.—Upper Silurian 
(g 1 ); Chotecz, Bohemia. [Royal Bohemian Museum.] 
Coccosteus fritschi, J. Barrande, ibid. (1872), p. 639, pi. xxx. 
figs. 1-6.—Upper Silurian (g 1 ); Schwagerka quarry, 
Hlubocep, Bohemia. [? Aspidichthysd) [Royal Bohemian 
Museum.] 
Coccosteus obtusus, C. H. Pander, in A. von Keyserling, Reise in 
das Petschoralaud (1846), p. 292 b. —Devonian; River 
Uchta, Petchora Land. 
Coccosteus obtusus , A. von Koenen ( non Pander), Abh. phys. Cl. 
k. Gesell. Wiss. Gottingen, vol. xxx. (1883), p. 10 ; Yer- 
handl. natur. Yerein. preuss. Rheinl. etc. vol. xliii. (1886), 
p. 55, woodc. 1, 2 : Brachydeirus obtusus, A. von Koenen, 
torn. cit. (1883), p. 21.—Upper Devonian; Wildungen, 
Bicken, and Miillenborn, Eifel. [? Holonema. ] 
Coccosteus primus, J. Barrande, tom. cit. (1872), p. 640, pi. xxix. 
figs. 1, 2.—Upper Silurian (f 2) ; Konieprus, Bohemia. 
[Royal Bohemian Museum.] 
Genus BRACHYDIRUS, A. von Xoenen. 
q [Zeitschr. deutsch. geol. Ges. vol. xxxii. 1880, p. 675, and Abh. 
t^**'*^ phys. Cl. k. Ges. Wiss. Gottingen, vol. xxx. 1883, p. 20 (as 
^ *(. , subgenus of Coccosteus). ] 
^ ,'^u.cA jf/iShield of head and abdominal region closely resembling that of 
Coccosteus , but more laterally compressed. Pectoral limbs represented 
by a slender, hollow spine. (A. von Koenen .) 
Some doubtful diagnostic characters are also noticed by von 
Koenen in the suture between the cranial and abdominal shields. 
As remarked by Traquair l , the presence of a pectoral spine suffices, 
to distinguish this form generically from Coccosteus, in the typical 
species of which no such appendage exists. 
The following species are recognized:— 
Brachy clivus bickensis : Coccosteus bickensis, A. von Xoenen, 
Zeitschr. deutsch. geol. Ges. vol. xxviii. (1876), p. 667, 
and ibid. vol. xxxii, (1880), p. 673, and Abh. phys. Cl. k. 
1 Geol. Mag, [3] vol. vii. (1S90), p. 23.3. 
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