﻿202 



AXIIAKCHA. 



Tremataspis schrenki (Pander). 



L866. Cephalaspis sehrenkii, C. H. Pander, Foss. Fische Silur. Syst. 

 p. 47, pi. iv. fig. 2. 



(?) 1856. Stigmolepis owenii, C. II. Pander, ibid. p. 53, pi. v. fig. 7. 

 1 B56. Odontotodus rootsikuellensis, C.H. Pander, ibid. p. 75, pi. vi. fig.21. 

 I860. Tremataspis schrenkii, F. Schmidt, Verhandl. russ.-kais. mineral. 

 Ges. 'St. Petersburg, [2] vol. i. p. 233, pis. v., vi. 



Ttype. Fragment of shield ; School of Mines, St. Petersburg. 



Shield depressed, gently rounded, longer than broad; anterior 

 margin obtusely rounded ; lateral margin, and the anterior margin 

 of the ventral shield, coarsely crenulated ; posterior margin slightly 

 excavated. Orbital opening situated at about one-fifth of the total 

 length of the shield from its anterior extremity ; postorbital " va- 

 cuity " antero-posteriorly elongated, pear-shaped ; a faint median 

 longitudinal ridge towards the hinder end of the shield. 



Form. 4' Loc. Upper Silurian : Kootsikiille, Isle of Oesel. 



Xot represented in the Collection. 



The so-called Chordate genus and species, Mycterops ordinatus, 

 E. D. Cope, Amer. Naturalist, 1886, p. 1029, woodcut, from the 

 Coal-measures of Pennsylvania, is founded upon an imperfect shield 

 of an Eurypterid in the collection of Prof. E. D. Cope, Philadelphia 

 (A. S. Woodward, Geol. Mag. [3] vol. vii. 1890, p. 395). 



Order III. ANTIARCHA. 



Exoskeleton consisting of calcifications with bone-corpuscles, and 

 invested with a more or less continuous superficial layer of ganoine. 

 Dermal sense-organs occupying open grooves upon the exoskeleton. 

 Dorsal and ventral shields consisting of several symmetrically 

 arranged pieces, and the head articulated with the trunk ; orbits 

 close together. Paired fins represented by paddle-like appendages 

 covered with dermal plates. 



The only family of this order as yet determined with certainty 

 is that of the Asterolepidae. 



