XXI. CRABRO. 159 
base, and the anterior tarsi also densely fimbriated on the edges, 
those as well as the intermediate more yellow, in other respects 
exactly like the 9 ; the abdomen subcylindrical, narrower, and 
more elongate. 
$ g in many Cabinets. 
t4++ If the form of the anus and a difference of general 
habit constituted claims to generic separation, it is clear 
that St. Fargeau ought to have removed this species from 
his genus Crossocerus; for, in the former peculiarity, it is 
more evidently distinct from the rest of this genus of his 
than are his Corynopus and Physoscelus from each other. 
This and the following species, which latter appears hitherto 
unknown, form, by their distinctly clavate abdomen, with 
the C. dimidiatus a direct link to division B., contain- 
ing the petiolated C. rufiventris and C. tibialis, which 
further proves the inutility of St. Fargeau’s elaborate dis- 
tribution, there being, throughout all the species, direct 
points of contact which connect them together, although 
they cannot be arranged in a consecutive series. If in the 
multitude of modes of natural arrangement that have been 
proposed I might be allowed to suggest the intercalation 
of one, I should consider this genus Crabro a central 
group, whence, from the diversity of its forms, all the rest 
of the fossorial Hymenoptera would radiate ; yet, even then 
it will be found that this planet has its satellites, with occa- 
sionally a comet to cross their orbits! Nature is too Protean 
to be bodiced. 
Sp. 20. capitosus. N. Sp. 
niger, capite quadrato, abdomine clavato, metathorace levi, tibiis 
posticis valde incrassatis 2. 
length 33 lines. 
Entirely black: head large, subquadrate, smooth and shining ; 
