56 



PISCES 



CLASS I 



Order 4. ANTIARCHA. Cope.i 



Dermal armour fused into large plates on the head and abdominal region. Exo- 

 sJceleton consisting of calcifications with h(me corpusdes, and invested with a more or 

 less continuous layer of ganoine. Dermal sense organs occupijing open grooves on the 

 exoskeleton. Dorsal and ventral shields consisting of several symmetrically arranged 

 pieces, and the head articulated loith the trunh. Orbits close together. Ä pair of 

 paddle-like pectoral appendages, invested in dermal plates, articulated with the 

 anterior ventro-lateral plates of the trunh. Median fins not continuous. 



The bony plates of the Antiarcha consist of three layers with numerous 

 bone cells, the middle layer traversed by large canals and lacunae, while the 

 outer and inner layers exhibit a more compact texture. 



Family 1. Asterolepidae. Traquair. 



Exoskeleton robust and tuberculated. Dorsal and ventral shields of trunh firmly 

 y the lateral plates. Inter orbital piece not ßxed. A fair of paddle-lihe 

 appendages, completely encased in dermal plates, movably articulated by a complex 

 Joint with the anterior ventro-lateral plates of the trunh. Tail heterocercal, and one 

 small dorsal fin. Devonian. 



Pterichthys, Ag. (Pterichthyodes, Bleeker), (Figs. 108, 109). From 3 to 20 



Fig. 108. 

 Pterichthys milleri, Ag. Restoration from above {A), below (B), and in side view (C). Lower Cid Red Sand- 

 stone ; Scotlaud. ap, Pectoral api)endages ; j, Articulation ; op, Operculuni ; orb, Orbit (after Traquair). 



cm. in length, with a small head, which is rounded in front, a broad and deep 

 trunk flattened below, and a scaly tail. The upper surface of the head is 



^ Pander, C. H., Die Placodermen des devonischen '«Systems. St. Petersburg, 1857. — Traquair, 

 R. H., Ann. Mag. Nat. Hist. ser. 6, vol. II. 1888 ; and'Mon. Palaeont. Soc, 1894. 



