194 Description of JYew and Interesting Animals. [Oct., 



The insect is not strictly a Cecidomyia, the posterior vein of 

 the wing being interrupted, the basal portion sending a detlected 

 filament (which does not seem to be hollow,) to the middle of the 

 posterior margin. The disrupted parts of the posterior vein pass 

 and run parallel to each other for a short distance, the apical por- 

 tion being the more anterior. 



Two species of minute parasitic Hymenoptera, destroy a great 

 many individuals of this insect, which, in conjunction Avith Odon- 

 tota'scutellaris celiv., has for the last two years killed the foliage 

 of robinia, in south-eastern Pennsylvania, so that the trees present 

 the appearance of having been destroyed by dry-weather, the 

 brown leaves remaining upon the tree. This happens chiefly in 

 August. 



REPORT ON THE SUPPOSED IDENTITY OF ATOPS TRILINE- 

 ATUS, iEmmons,) WITH TRIARTHUS BECKII. 



BY S. S. HALDEMAN. 



Made to the Association of American Geologists and Naturalists, during the 

 session of September, 1847. 



Since the publication of Prof. Emmons's work upon the Ta- 

 conic System, there have been several discussions relative to the 

 views offered in that work; and at the last meeting of the Asso- 

 ciation in New York, when the subject was again brought forward, 

 an argument was drawn from the supposed identity of the above 

 named trilobites. A committee was then appointed to investigate 

 the question, and the present report is offered as the result. The 

 specimens submitted for examination, are both imperfect, particu- 

 larly that of Jltops, so that it is impossible without better mate- 

 rials, to institute a rigitl comparison between them, or even .to 

 determine the genus of the latter. Moreover, the proper external 

 surface in the Atops, seems to be wanting; and but four abdomi- 

 nal segments remain. The comparison is thus restricted to these 

 segments and the cephalic shield. The outline of these portions 

 taken conjointly, nearly correspond in the Triarthus to a square, 

 and in the Atops to a transverse parallelogram, the sides of which 

 are nearly in the proportion of four to five. The medial lobe of 

 the shield in the former has impressed lines converging backwards, 

 whilst the traces of these in the latter are transverse. The follow- 

 ing table presents the comparative characters offered by the two 

 specimens. 



