58 PISCES CLASS I 



Microbrachius, Traquair. 31. dicki, Traquair, from Lower Old Eed Sandstone, 

 Caitliness and Orkney. 



Bothriolepis, Eichw. {Pamphr actus, Placothorax, Homothorax, Olyptosteiis, Ag.). 

 Armour nearly as in Pferichthys, but the pectoral appendages reaching back- 

 wards beyond the body shield, and the hinder mucous canal commissure on the 

 head V-shaped. Tail unknown, probably not scaly. An Upper Devonian 

 genus, known from N.-W. Russia, Scotland, England, Canada, and Penn- 

 sylvania. Remarkably fine examples of the armour of B. canadensis, Whit- 

 eaves, 0*20 m. in length, from Scaumenac Bay, Province of Quebec, Canada. 



? Ceraspis, Schliiter ; Belemnacanthus, Eastm. Middle Devonian ; Eifel. 



Incertae Sedis. 



Macropetalichthys, Norwood and Owen. Plates of cranial shield fused 

 together in adult ; orbits completely enclosed in the shield ; sensory canals 

 forming large tubular excavations in the bone, opening at the external surface 

 by a continuous narrow slit or a series of pores. Jaws and other parts of 

 the skeleton unknown. Middle Devonian (Corniferous Limestone) ; U.S.A. 

 Also Upper and Lower Devonian of Eifel. 



Asterosteus, Newb. Known only by the flattened and elongated cranial 

 shield, which has the constituent elements fused in the adult. Orbits placed 

 far forwards and forming- broad notches. Corniferous Limestone ; Ohio. 



Sub-Class 3. ARTHRODIRA. Smith Woodward. 



Early Palaeozoic fishes tvith persistent notochord, and endosheleton superficially 

 calcified. Head and trunk armoured with symmetrically arranged bony plates, some of 

 ■which are traversed by sensory grooves ; head shield movably articulated by a pair of 

 ginglymoid joints with the body shield. Paired fins rudimentary or absent. 



The Coccostean fishes were originally grouped by M'Coy with Asterolepis 

 and Pterichthys in the " family Placodermi," and they are included by Pander 

 in his " Placodermen." The resemblance between their jaws and those of the 

 existing Dipnoi was pointed out by Newberry and Traquair ; and they Avere 

 provisionally regarded as an order of Dipnoi by Smith Woodward. Dean 

 elevates them to the rank of an independent class, removing them from Pisces 

 on the ground that their jaw elements are merely dermal ossifications, and 

 are not articulated with the skull. 



Family 1. Coccosteidae. Smith Woodward.^ 



Head shield comprising three pairs of lateral plates, one large median occipital 

 plate, ami two symmetrical pairs of plates in front of the latter, the foremost pair 

 surrounding one or two small median plates. Orbits lateral ; nasal openings small 

 and far forwards ; de.ntal plates movable, toothless, or provided with cusps of dentine. 

 Trunk with a large median dorsal plate often bearing a longitxbdinal median keel on 

 its under surface ; also two pairs of lateral plates, the anterior with a pair of articular 



^ Traquair, R. H., On the Structure of Coccosteus decijjiens, Ag. (Auu. Mag. Nat. Hist. ser. 6, 

 vol. V. p. 125), 1890.— i>t'«H, B., Palaeontological Notes (Mem. N. Y. Acad. Sci. vol. II. pt. 3), 

 1901. — Eastman, C. R., Some uew points in Dinichthyid Osteology (Amer. Nat. vol. XXXII. p. 

 747), 1898. 



