﻿'204: ARTHI10D1RA. 



Dermal plates of Placoderins, 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. figs. 3, 4, 6-8.— Upper Silurian 

 (gl); Chotecz, Bohemia. [Royal Bohemian Museum.] 



Coccosteus fritschi, J. Barrande, ibid. (1872), p. 639, pi. xxx. 

 figs. 1-6. — Upper Silurian (g 1); Schwagerka quarry, 

 Hlubo^ep, Bohemia. [? Aspidichihys.~\ [Royal Bohemian 

 Museum.] 



Coccosteus obtusus, C. H. Pander, in A. von Keyserling, Reise in 

 das Petschoraland (1846), p. 292 6. — Devonian ; River 

 Uchta, Petchora Land. 



Coccosteus obtusus, A. von Koenen (non Pander), Abh. phys. CI. 

 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, torn. cit. (1872), p. 640, pi. xxix. 

 figs. 1, 2. — Upper Silurian (f 2) ; Konieprus, Bohemia. 

 [Royal Bohemian Museum.] 



Genus BRACHYDIRUS, A. von Koenen. 

 [Zeitschr. deutsch. geol. Ges. vol. xxxii. 1880, p. 675, and Abh. 

 phys. CI. k. Ges. Wiss. Gottingen, vol. xxx. 1883, p. 20 (as 

 subgenus of Coccosteus).'] 



Shield 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 : — 



Brachydirus biclcensis : Coccosteus bickensis, A. von Koenen, 

 Zeitschr. deutsch. geol. Ges. vol. xxviii. (1876), p. 667, 

 and ibid. vol. xxxii. (1880), p. 673, and Abh. phys. CI. k. 



1 Geol. Mag. [3] vol. vii. (1890), p. 235. 



