1856. Cephalaspis schrenkii, C. H. Pander, Foss. Fisclie Silur. Syst. 
p. 47, pi. iv. fig. 2. 
(?) 1856. Stigmolepis owenii , C. H. Pander, ibid. p. 53, pi. v. fig. 7. 
1856. Odontotodus rootsikuellensis, C.H. Pander, ibid. p. 75, pi. vi. fig. 21. 
1866. Tremataspis schrenkii, F. Schmidt, Aerhandl. russ.-kais. mineral. 
Ges. St. Petersburg, [2] vol. i. p. 233, pis. v., vi. 
Type. Fragment of shield ; School of Mines, St. Petersburg, i 
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 ” anter.o-posteriorly elongated, pear-shaped; a faint median 
longitudinal ridge towards the hinder end of the shield. 
Form. Sf Loc. Upper Silurian : Kootsikiille, Isle of Oesel. 
Not represented in the Collection. 
The so-called Chordate genus and species, Mycterops ordinal us, 
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). 
CU*. ,<?*}, p-' e r 
Oo U PS!/US! JoJ-*- it?*’ 
pm- 
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 Asterolepidse, 
__ /r/ t’np/-*'Sf ? CP • 

