﻿A.NTIABCHA. 



minor, L. Agassiz, Poiss. Foss. vol. i. (1844).. p. xxxiii 



(name only). — Devonian ; Riga and St. Petersburg. Upper 



Old Red Sandstone ; Elgin. [Original of Agassiz, pi. xxx. 



fig. 11, considered as probably referable to Asterolepis 



concatenata by E. von Eichwald, Leth. Rossica, vol. i. 



(1860), p. 1510.] 

 Asterolepis speciosa, L. Agassiz, op. cit. (1845), pp. 93, 146, 



pi. xxx. fig. 10, pi. xxx. a. fig. 4. — Devonian; Yoroneje, 



Russia. 

 Asterolepis wenhenbachii, C. Koch, Yerhandl. naturh. Yerein., 



Bonn, vol. xxix. (1872), Correspond, p. 85 (name only). 



— Devonian : Eifel. 



Genus PTERICHTHYS, Agassiz. 

 [Poiss. Foss. Y. G. R. 1844, p. 6.] 



Head and trunk broad, but much elevated, the scutes ornamented 

 with tubercles; tail covered with rounded or hexagonal scales, 

 slightly imbricating. Lateral sensory canals on the upper aspect of 

 the head united by an anterior transverse commissure crossing the 

 premedian plate, and a posterior one directly crossing the median 

 occipital ; anterior median dorsal plate overlapping the anterior 

 dorso-lateral, overlapped by the posterior dorso-lateral. Pectoral 

 appendages shorter than the armoured trunk, segmented into a 

 distal and proximal portion ; marginal scutes of proximal portion 

 separated above and below by a median " anconeal " element ; 

 marginal and central scutes of distal portion few. A single small 

 median dorsal fin, with large anterior fulcral scales, but apparently 

 no fin-rays. 



The exoskeleton of this genus is now tolerably well known, 

 owing especially to the researches of Miller, Pander, and Traquair ; 

 and the accompanying restorations (fig. 33, A, B, C) are those of the 

 last-named author. Fig. A represents the dorsal aspect, and fig. B 

 the ventral aspect, while fig. C is a side view. The exposed margins 

 of the plates of the trunk are shown by thickened lines, while the 

 amount and direction of their overlap are indicated by the thin 

 lines. Sensory canals, both upon the head and trunk, are marked 

 by double dotted lines. We would only add that the large inferior 

 expansion of the caudal fin is omitted in the third figure (compare 

 PI. YI. fig. 3, x) ; and for the details of the hard parts in the 

 orbital opening, reference must be made to some of the specimens 

 described below, notably the original of PI. Y. fig. 2. 



The cranial shield is small compared with the armour of the 



