Ve 
Dreteura Dexavr. Green. Casts No. 30, 31, and 
| Fi as 8 & 9. { f. r 
a a: 
Clypeo lunato punctato; abdomine quatuordecim 
articulis duplicibus vix lobatis; cauda suborbicularis 
limbo lato convexo integerrimo; oculis oblique de- 
flexis. 
The buckler is subtriangular, and covered with 
eranulations; the anterior portion of our specimen 
being mutilated, we cannot determine its form exactly. 
The cheeks are very prominent, and swell up gradually 
towards the oculiferous protuberances, which are ob- 
lique, and marked at their apex with a depression, 
so as to give them an annular appearance. The abdo- 
men is crossed by fourteen double distinct articula- 
tions, not interrupted in their course, by the two 
longitudinal furrows, so common in most of the tri- 
lobites; but owing to certain curves or irregularities 
in the ribs near their lateral termination, a trilobate 
appearance may in some specimens be detected. 
Tail suborbicular, convex, and covered with a thick 
epidermis. | : 
The specific name of this species was given in com- 
pliment to Dr. James E. Dekay, of New York, whose 
valuable paper on the genus Isotelus, first directed 
my attention to the American trilobites. . 
The D. Dekayi has been found in several districts 
of the United States; at Lockport in the State of 
New York, it is not uncommon. The small speci- 
men from which our cast of the abdomen and caudal 
