222 
AXTIARCHA. 
ornament both of the ventral plates and caudal scales is 
shown in impression. Purchased , 1861. 
(iv.) Cromarty. 
19052, 19055, 19059. Three imperfect examples of the trunk, 
ventral aspect, the first also showing traces of the tail, 
and the third, of the head. Purchased , 1845. 
19804 a. Imperfect specimen displaying the inner aspect of the dorso¬ 
lateral and median dorsal plates, and characteristic por¬ 
tions of the expanded appendages. In the orbital opening 
the “ os dubium ” is distinctly separated from the right 
orbital plate, and there is a trace possibly of an anterior 
plate in advance of the former. The scales of the tail are 
observed to be tuberculated. Purchased , 1845. 
47870. Much crushed trunk and appendages, in counterpart, showing 
ornamentation. Purchased , 1877. 
Pterichthys rhe nanus, Beyrich. 
1855. Physichtkys hoeninghausi , H. von Meyer {errore), Palaeontogr. 
vol. iv. p. 80, pi. xv. fig. 7. [Anterior median dorsal plate ; Cam¬ 
bridge Museum, Mass.] 
1877. Pterichthys rhenanus , E. Beyrich, Zeitschr. deutsch. geol. Gesell. 
vol. xxix. p. 751, pi. x. 
Type. Dermal armour of trunk ; Berlin Museum. 
Inferior surface of carapace broadly ovate. Anterior median 
dorsal plate as broad as long, extremely elevated, the longitudinal 
ridge bent at a right angle slightly behind the middle point; posterior 
median dorsal plate two thirds as long as the anterior median. 
Form, Loc. Devonian : Gerolstein, Eifel. 
Not represented in the Collection. 
Dermal plates of Antiarcha (and probably other Chordate types), 
too imperfect for satisfactory determination, have also been assigned 
to Pterichthys under the following names :— 
Pterichthys arenatus , L. Agassiz, Poiss. Eoss. Y. G. B. (1845), 
p. 133, pi. xxx. a. fig. 3.—Devonian ; St. Petersburg. 
Pterichthys cellulosus , C. H. Pander in A. von Keyserling, Beise 
in das Petschoraland (1846), p. 29 2a. —Devonian; Pet- 
chora Land, N.E. Bussia. 
Ptei 'ichthys elegans , C. H. Pander, Monogr. Foss. Fische Silur. 
