THE CANADIAN P]NTOMOLOGLS:y. 179 



f 2. Pronotum with distinct lateral and median 

 carinae, the latter sometimes weak, 

 gi. Lateral carinne of pronotum parallel 



or subparallel Steiroxys. 



g2. Lateral carinpe approximated in 

 middle of anterior half of pronotum, 

 so as to narrow the dorsum by 



nearly one-half Idionotus. 



d2. Fore tibiae with four spines above on outer margin, 

 e I. Descending lobes of pronotum declivent, 



the dorsum narrow Clinoplcura. 



Descending lobes of pronotum narrow, 



e 2. 



c 2. 



the dorsum broad Plagiostira. 



Fore tibiee'with only one spine above on outer mar- 

 gin, situated at apex Ateloplns. 



Engoniaspis, Brunner (Re'v. Syst. Orth., 185). 



No species of this genus has yet been described. Brunner founded it 

 upon a species from Missouri, in his collection, which is very likely the 

 same as that represented in the Riley collection of the U. S. National 

 Museum by an imperfect specimen from an unknown locality. 



Atlanticus (aTAavTt/cos^) Gcn. nov. 



This generic name is proposed for the only species of Decticidce 

 (except some species of Orchesticus) that occur on the Atlantic slope 

 of North America, and are confined to that district, or at 

 least to the region east of the Mississippi. They resemble the 

 European Thamnotrizon in general appearance, but have a spined 

 prosternum. They are closely related to Engoniaspis, but the males are 

 not apterous, the prosternal spines are well developed and the cerci 

 are not depressed. Three species are known to me, two of them long 

 ago described by Burmeister under the names of Decticus dorsalis and 

 D. pachymerus (one of them, probably the latter, afterwards described by 

 Walker as Decticus derogatus), and a third, which appears to be a more 

 southern and robuster form, represented in my collection by two pairs 

 coming from North Carolina to Blorida. These species may be thus dis- 

 tinguished : — 



Inner tooth of cJ cerci short ; lateral carinae of pronotum sharply 



pronounced. 



