246 
Psyche 
[September 
It has taken almost 80 years for acquisition of the above data about 
these two groups of insects, though they are not rare in Paleozoic 
deposits. This slow process becomes more understandable after con- 
sidering the character and nature of preservation of the projections. 
Protruding above the body in life, they tended to become hidden by 
the superimposed sediment rather than become compressed at the same 
level as the body itself during fossilization. The broken and usually 
more sclerotized bases of the projections are not distinguishable from 
spines or tubercles and are mostly inconspicuous. Finally, in a ma- 
trix which does not preserve chitin, the imprints of the projections 
are vague. 
During my study, the projections were thoroughly examined for 
connections with the insect’s body. In the matrix capable of pre- 
serving chitin (e.g. Commentry shale), the projections have the same 
brown color as the terga. Their surface is covered with a rugosity 
similar to that on the body (Mazon Creek, Illinois) or with a minor 
rugosity and scattered sockets of setae (Obora, Moravia). In Mon - 
steropterum moravicum } the surface of the projections is identical to 
that of the legs. The arrangement of the projections is regular and 
probably characteristic for all genera within a family (I have found 
this to be true so far for Bardohymenidae, Protohymenidae and Mis- 
chopteridae). The width of the projections varies with the size of 
specimens; their arrangement is bilaterally symmetrical. The above 
mentioned features exclude the possibility that the outgrowths are 
parasitic organisms or fungi. 
These projections in the Megasecoptera and Palaeodictyoptera ap- 
pear unique among insect orders, and their function remains ob- 
scure. However, several features suggest that they might be homo- 
logous to certain tergal structures of Odonata. In all Recent Odo- 
nata, there is a transverse ridge at each end of the tergum, the 
anterior and posterior transverse carinae (Walker 1953, p. 18). The 
former is inconspicuous, but the posterior carina is a distinct ridge 
bearing a row of small tubercles or denticles. By the position and 
arrangement in rows, the projections in Megasecoptera and Palaeodic- 
tyoptera are very suggestive of the prolonged and enlarged carinal 
denticles of Odonata. Their function, of course, presents a com- 
plicated problem, which can hardly be solved with fossil material. 
Order Megasecoptera 
Family Bardohymenidae Zalessky 
Type Genus: Bardohymen Zalessky, 1937. 
This family was erected by G. Zalessky (1937) and redefined by 
