sa cl dal 
FOSSIL DIPTERA. 5 
family, especially in specimens, but not so in species, for as many as 
a thousand specimens have been alone found at Florissant, according 
to Scudder. But amongst these thousand there are only fifteen to 
twenty species. 
Bibio is one of the most plentiful genera, and is abundant at 
Oeningen. They are rare in amber, but abundant in the Tertiary 
rocks. | 
Fam. Simudide.—In the Purbecks of England two species of this 
family have been preserved, namely, Stsmulium humidum and Simu- 
lium priscus. 
Others are also found in the Tertiaries. 
Fam. Mycetophylide.—This family, again, is found in the Mesozoic 
period, several genera having been described by Brodie under the 
names Platyura = Adonia of Giebel, and Macrocera = Sama of Giebel. 
Another genus, Z/zras, now extinct, has been figured by Westwood. 
In the Tertiary formations these flies appear abundantly, many of 
which are now extinct as generic types. They are found both in the 
amber and Tertiary rocks, the species being generally distinct in 
the two modes of preservation. For instance, Sciobia, Aclada and 
Heterotricha are genera peculiar to the amber, not being found in the 
rocks. 
A great number of species have been described, and from very 
wide localities, especially from Aix, Utah, Wyoming, Oeningen, 
Florissant, and England. 
Fam. Cecidomyide.—Members of this family have mostly been 
found in amber, there being no record of them in Mesozoic times. 
Fam. Syrphide.—It is somewhat doubtful if this family is really 
represented in time earlier than the Tertiary. ‘Two species have 
been referred to the Syrphidze from the Mesozoic rocks; one 
from the renowned rocks of Solenhofen, which, according to Weyen- 
bergh, is a Chezlosta, another has been figured by Brodie from the 
Purbeck that may possibly belong here, but being only fragmentary, 
its true nature remains very doubtful. The following genera are 
present in the Tertiary beds, viz., Xylota, Chetlosia, Volucella, Rhingia, 
Sprphus, and Eristalis. 
The following table, taken from part of Scudder’s table of the 
Geological distribution of insects in his systematic review of their 
fossil remains, shows the range and time of origin of the four great 
divisions of Diptera. 
