22 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
specimen by pressing backward against the anterior claspers, the 
penis and posterior claspers being throuTi forward. But neither pres- 
sure forward nor backward on the claspers serves to bring the penis 
back. This movement is probably controlled by muscles connected 
with the penis as the claspers release their hold when pressure is 
exerted backward upon the former. 
The structure of the penis is comparatively simple compared 
with that of Sarcophaga carnaria as presented by Bottcher (Deutsch. 
Ent. Zeitschr., 1912, p. 533). This is true of the genus throughout, as 
well as of these two species. The penis of the species under discussion 
is not divisible into basal and distal portions as is so often the case 
among the species of Sarcophaga, but consists of a simple stock or 
stem that becomes enlarged distally. It shows but two distinct 
sclerites, an anterior and a posterior (PI. 6, fig. 41, abp., ppn.). The 
former is short and separated from the latter by a partially chitinized 
membranous region as shown in the figures. The posterior plate 
basally extends beyond the anterior (PI. 6, fig. 43) and articulates with 
the apodeme, while beyond the distal end of that plate it becomes 
enlarged, ending in paired lateral knobs, and below these each side 
is extended around to the anterior surface of the penis though they do 
not meet. The anterior plate is undoubtedly the same as Bottcher's 
"ventrale Chitinspange des Stieles," but the posterior would include 
several of his subdivisions of the penis of S. carnaria. The distal 
enlarged part of this plate is not closed anteriorly but a sort of cavity 
is formed. From this cavity three processes extend forward, an upper 
median (PI. 6, fig. 40, mp.) and below it two paired laterals (PI. 6, 
fig. 40, Ip.). The small median process passes out between the anterior 
extremities of the lateral extensions of the posterior plate; outwardly 
it is bilobed. Each lateral process may be described as consisting of a 
basal part bearing two lobes. The basal part is attached inside near 
the base of the cavity. One lobe extends forward and reaches beyond 
the median process, the other backward and is often concealed within 
the cavity; the former is often the only one which can be seen. All 
three processes are partly membranous and supported by chitinous 
plates. The changes which take place in their structure and relative 
position are easily traced in the several species of Ravinia described 
in this paper. There is no part of the penis of S. carnaria which I 
would ffeel safe in considering as equivalent to the median process above 
described. Possibly Bottcher's "medialen Klappen" will correspond 
