214 [Decembee, 



14. T. atr ox, elongafus, ovafas, niger, thorace latitudine duplo breviore, late 

 marginato, confertim punctato, breviter setoso, subcanaliculato ? lateribus late 

 rotundatis, elytris striis duplicatis crenatis, interstitiis uniseriatim flavo-setosis. 

 Long. -33. 



One specimen, found near Long's Peak. The setae of the elytra arise from 

 small murieated punctures. The anterior tibiae are more tiilated than in the 

 other species; the terminal tooth is very much rounded, and above it are two 

 or three sinuosities indicating other teeth. The form is that of T. variolatus 7 

 but larger. 



Omorgtjs Er 



This genus, described at length in Wiegmannn's Archiv., (13, 111) and referred 

 to in Erichson's Ins. Deutsch. (925), contains the largest species of our native 

 Trogidae. It difFers from Trox by the corneous prominent ligula, by the first 

 joint of the labial palpi being longer than the second, and finally by the terminal 

 hook of the maxillae being cleft, and the second hook being single. (In Trox 

 the terminal hook is usually trifid.) As these characters are difficult, certain 

 differences in appearance may be made use of to separate the two genera. Thus 

 in Trox the sides of the thorax are strongly ciliated, and broadly regularly 

 rounded, while in Omorgus the sides are hardly ciliate, and are frequently ir- 

 regular, and sometimes toothed : the eyes of our native species of Trox 

 are reticulated, and the posterior tibiae toothed ; while in Omorgus the eyes 

 are smooth, and the posterior tibiae in our native species without teeth. Of 

 these habitual characters, reliance can be placed absolutely upon none but the 

 structure of the sides of the thorax, as according to Erichson, species of Trox 

 occur in which the eyes are smooth and the posterior tibiae toothless. Our species 

 may be divided thus : 



A. Corpus dpterum ; thorace bullis nitidis or nato, 



1. O. texanus, apterus niger, convexus, thorace cataphraeto valde in- 

 aequali, lateribus rotundatis ante basin subincisis, elytris seriatim grosse punc- 

 tatis nitidis irregulariter ccelatis. Long. 8. 



Eagle Pass, Texas, collected by Mr. Schott, under Major Emory, of the 

 U.S. and Mexican Boundary Commission, and also by Lieut. Haldeman. This- 

 species is larger than 0. scutellaris, and the lines of punctures on the elytra are 

 better marked ; but except in the form of the sides of the thorax, there appears 

 to be no special difference ; as in that species, the posterior outer angle of the 

 large four-angled bulla each side of the dorsal channel is produced. 



2. 0. scutellaris, apterus niger, thorace cataphraeto, valde insequali ? 

 lateribus rotundatis, elytris seriatim minus distincte punctatis, transversim 

 ccelatis, interstitiis subquadratis, subaequaliter parum elevatis. Long. *6 65 



Trox scutellaris Say, Journ. Acad. Nat. Sc, 3, 23S. 



Kansas Territory near the mountains : New Mexico, Mr. Fendler : abundant. 



3. O. suturalis, apterus niger, thorace cataphraeto, valde inaequali? 

 lateribus rotundatis, elytris minus distincte seriatim punctatis, transversim 

 ccelatis, interstitiis inaequaliter magis elevatis, sutura costata. Long. -63. 



Texas Mr. Schott, two specimens. Distinguished from the preceding by the 

 more elevated and irregular shining spaces of the elytra, and by the suture being 

 elevated in the form of a eosta. 



4. O. umbonatus, apterus niger, thorace cataphraeto, valde inaequali? 

 lateribus rotundatis, elytris minus distincte seriatim punctatis, interstitiis trans- 

 versim ecelatis, alternatim magis elevatis. Long. *65'. 



Texas, Messrs. Schott & Clark. Also allied to 0. scutellaris, but besides the 

 inequality of the rows of elevations of the elytra, the four-angled bulla each side 

 of the dorsal channel of the thorax has the posterior outer angle not produced? 

 aad almost obtuse. The body is also more elongated. 



