Fusson'al Hymenoptera of North America. 47 



from Oxyhelm, the sole representative of the third group, Pompili- 

 fonnes. he passes to the Crabronidse Speci/ormes, headed by Dasy- 

 proctnx. passing by Rhopalum and terminating in Trypoxylon, which 

 leads to the next Family Pemphredonidx. This last group we accept as 

 well circumscribed and natural. Next follows the MelUnidx repre- 

 sented by Mellinus alone. Equivalent to this are the Philanthidse, 

 headed by Diamma Dahlb., and Dide&mus King and Erich., which 

 with Anthophilus King MSS., and SimblephHus Jurine, share the 

 fate of .St. Fargeau's genera and Dahlboin's Ectcmnius and Entomog- 

 nathus. 



The Nyssonida3 are distributed in the Larridse, where, in his ar- 

 rangement, are to be found Xi/sson and Gort/tes heading the group, 

 but separated widely from the Crabronidas (emend.) by the Beinbe- 

 cidae. 



Dahlbom's arrangements is interesting as exhibiting the analogous 

 forms of these lower members of a group to other entire groups of a 

 still more degraded position, such as the Spheciform Crabronida3 repre- 

 sented by Trypoxyltm which correspond to the lower family Sphegidoe 

 Dahlb. The Pompilidai are represented by N'rtcln. He also considers 

 as parallel groups Pemphredou and Crossoccrus, Bhpharipus and Mel- 

 linus, Thyreopus and Bcmbex while Crabro is offset by jSysson and 

 Cerceris. 



The best point in Dahlbom's classification is his admitting and limit- 

 ing the Pemphredonidae. 



Mr. F. Smith's arrangement, published in 1856,* seems to be based 

 upon Shuckard's arraugement, with judicious modifications. His ar- 

 rangement of the Crabronidse is the same except in placing Psen next 

 to Cerceris, and inserting Ccmouus. Ceratophorus and Diodontus, in 

 descending order, between Psen and Mimesa, which seems unwarranta- 

 ble, as these two genera are most closely connected by some species de- 

 scribed by us below. He closes the groups with Oxyhelus, Nitela and 

 Trypoxylon, which we have referred to the Nyssonida?. The Nysso- 

 nidie is a group quite different from Shuckard's limitation of it. It 

 is composed of twelve instead of three genera — Mellinus, Didineis, Aly- 

 son, Harpactus, Gorytes, Heltoryctes, Palarus, Sericophorus, jSysson, 

 Exeirus, Larra and Stizus, in descending order are its members. In 

 this arrangement we have the Nyssonidas more clearly circumscribed, 

 and rendered a less chaotic group than by any previous author. The 



-Catalogue of Hymenopterous Insects in the British Museum, Pt. iv, 1S56. 



