354 Dr. A. S. Packard, Jr's Revision of the 



hillum which ends in nearly as long a hook. In the two hinder pair 

 of legs the coxse are provided with an outer tubercle at tip, short, the 

 trochanters long and narrow, the femora somewhat angulated and 

 swollen ; middle tibiae with a small spur ; hind tibiae triquetal, with a 

 row of setiferous tubercles, with two very large spurs. First tarsal 

 joint a third longer than the remaining ones, or as long as all the rest 

 together. 



The $ has the fore-legs simple and rather slender, armed externally 

 with spine-like setaa, there being six setae on the basal joint; tibiae tri- 

 quetal, spined as usual. All the tibias have two unequal spines, the 

 last pair being much the longest, 1st joint of hind pair nearly as long 

 as the remaining ones together. 



Abdomen narrower than the thorax, slightly sub-pedunculated, 

 longer than the head and thorax together, a little broader in $ , which 

 has the tip broad, flat, triangular, the sides perfectly straight, not in- 

 curved as in Crabro ; tips of % broad, spatulate. 



This genus may easily be distinguished from Crabro by its elongated 

 body, the expanded fore-legs and antennae of the males, and the females 

 can invariably be distinguished from those of Crabro by the broad 

 spatulate, flattened triangular, supra-anal area, since iu Crabro cephal- 

 lotes of Europe and C. septentrionalis of this country, which, in many 

 of their characters, closely counect Crabro and Tliyreopus, the <j> tip 

 is mucronate, the spine being unusually compressed and deeply 

 grooved. 



In this genus the % head in front narrows rapidly toward the cly- 

 peal region, which is one-half as broad as the entire head behind the 

 middle of the eyes; in 9 it is much broader, but still much narrower 

 than in Crabro, as the head is much shorter, much broader than the 

 body, and more deeply excavated in front. The pterostigma, compared 

 with Crabro, is more distinct, the second median space is much shorter, 

 regularly diamond-shaped ; the 2nd median recurrent terminates on 

 the outer third of the length of the 1st sub-costal space, instead of at 

 the end, so that the form of this space is five-sided, rather than dis- 

 tinctly rhomboidal, as in Crabro. The submedian space is proportion- 

 ally shorter aud broader than in Crabro, and the outer side, or second 

 recurrent, is more obliquely curved outwards, where in Crabro it is 

 curved nearly transversely, and is slightly angulated. 



The female differs from Crabro in the shorter, more transverse, much 

 less cubical head. The antennae are slenderer toward the tips, propo- 

 deuui more produced, the enclosure well developed and distinctly tri- 

 angular, while it is nearly obsolete in Crabro. 



