lately discovered in the United States. 407 



detailed description of its various parts, it will perhaps be 

 advisable to mention those in which its more remarkable 

 monstrosities occur. In outward form this curious insect 

 strongly reminds one of some Crustacean genera, especially 

 of the " Horse-shoe Crab," Limulus Polyphemus. All its 

 limbs are very short ; the antennae, which consist of only 

 nine joints, are wide and flattened in order that they may 

 be the more easily withdrawn, together with the head, into 

 a deep and closely fitting recess in the prothorax ; the 

 head itself shuts into this recess more by the action of a 

 hinge than a true retraction ; it is very small, and wholly 

 without eyes, indeed all the ocular region is hollowed out ; 

 the organs of the mouth are large, and fully developed. In 

 these the only remarkable character exists in the origin of 

 the maxillary palpi, which rise from an elevated triangular 

 process in the middle of the upper surface of the stipes ; in 

 all other genera of this family these appendages are joined 

 to the upper angle of its outer edge. The development of 

 the prosternum and of the keel of the mesosternum is truly 

 monstrous, and unlike any existing form throughout the 

 whole order; of these the former is very much elevated, 

 excavated in front to receive the head, posteriorly it is pro- 

 duced into a wide and very long plate, convex, and deeply 

 bifid at its extremity, passing over the whole length of the 

 mesosternum and part of the metasternum, excavated on 

 each side near the base to allow the forward action of the 

 anterior coxae; the keel of the mesosternum, which is for 

 nearly half its length covered by the laminate process of 

 the prosternum, is anteriorly very much elevated, and carried 

 beyond the collar of the mesosternum, posteriorly it is ex- 

 panded over the intermediate coxae, and produced in a broad 

 spoon-shaped plate beyond the apex of the metasternum, 

 very wide, truncate and slightly emarginate at its extretnit}', 

 which is rather thickly clothed with long hair. The object 

 of this extraordinary formation, considered in connexion 



