12 
POPULAR SCIENCE REVIEW. 
Bay, Cariada, lias been described, and named after its discoverer, 
by Professor Lankester, in the Geological Magazine for 1870, 
p. 397, so that this curious genus must now be regarded as 
common to North America as well as to Britain. (Woodcut, Fig. 9.) 
An exceedingly narrow head-shield with enormously developed 
lateral horns, from the Downton Sandstone (Upper Silurian) 
Ludlow, is named Eukeraspis (Woodcut, Fig. 10). The outer 
border of the shield in this species is furnished with irregular 
marginal spines of various length. 
Two other British Osteostracous fish-shield shave been described. 
One of these, Auchenaspis (Woodcuts, Figs. 11 and 12) is repre- 
sented by two small shields (named A. Scclteri and A. Egertoni ); 
they are divided transversely into two parts: the anterior semi- 
circular and bearing the eyes, the posterior part oblong and much 
smaller. The other, named Didymaspis , represented by a single 
specimen (D. Grindrodi) is divided like the preceding, but the 
anterior part is without prominent cornua (Woodcut, Fig. 13), 
and nearly oval in outline. The former (. Auchenaspis ) occurs 
in the 44 Tilestones ” and Passage-beds at Ledbury and Ludlow ; 
the second ( Didymaspis ) is found in the Old Ked Sandstone of 
Ledbury. 
