66 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
respect. The characters of the bristles on the anterior face of the 
third femur, the lack of anterior and posterior ventral rows on the 
middle femur, the comparative length of the fourth and fifth tarsal 
segments, and the fact that the ventral plates increase in width 
posteriorly are probably the most important features. In some 
species the lower portion of each parafrontal plate seems to be some- 
what swollen, forming a sort of crest that bears the frontal bristles. 
The epaulets are deep brownish in color and normally slightly grayish 
pollinose outwardly, but the pollen frequently becomes rubbed off. 
In all our New England species the abdomen is elliptical in outline, 
the first genital segment in profile has a shallow depression just in 
front of the marginal bristles, and the posterior femur is more or less 
cylindrical. I have a species from Jamaica, however, in which the 
abdomen is distinctly conical, the first genital segment shows a pro- 
tuberance rather than a depression, while the posterior femur is 
subspindle-shaped. It also has a semimetallic luster. 
The color of parafrontals and genae varies from a grayish white to 
aurichalceous or brassy, but usually has a brassy tinge. The dusting 
of the first genital segment is not at all constant in color or extent. 
The penes are quite different from any found in Sarcophaga (I have 
not examined that of the Jamaican species). They show a distinct 
division into proximal and distal portions (base and head). The 
latter is divided into a basal portion and a smaller end piece that seems 
to be set within it; the basal part is prolonged forward into a process, 
which in B. latisterna is even longer than the main part of the penis. 
In B. bisetosa and B. fernaldi this process is somewhat shorter and 
bends backward tending to overlie the end of the penis. 
Chving to the variations in form and position assumed by the penes 
of the last two species, the figures presented will by no means fit every 
case, but unless other species are found showing still different forms of 
this structure its relative size is Specific in each case. The shape of 
the anterior and posterior claspers varies greatly and does not offer 
the sameness of form and relative size found among the species of 
Ravinia. The fourth ventral plates, however, are much alike, and 
show a distinct relationship. 
The several species described are very similar as regards external 
characters and their specific differences few. For this reason no 
discussion of these follows the specific descriptions, the important 
characters being presented in the introductory paragraph. 
