79 



DIPLEURA DEKAYI. Green. Casts No. 30, 31, and 

 Figs. 8 & 9. 



Clypeo lunato punctate; abdomine quatuordecim 

 articulis duplicibus vix lobatis; cauda suborbiculari; 

 limbo lato convexo integerrimo; oculis oblique de- 

 flexis. 



The buckler is subtriangular, and covered with 

 granulations; 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. Qekay, 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 



