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. Simtdidce. — In the Purbecks of England two species of this 

 family have been preserved, namely, SimuUuin humiduvi and Simu- 

 Ihim prisciis. 



Others are also found in the Tertiaries. 



Fam. Alycetophylidce. — This family, again, is found in the JNIesozoic 

 period, several genera having been described by Brodie under the 

 names Platyura = Adonia of Giebel, and Macrocera = Saina of Giebel. 

 Another genus, T/iiras, 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. Cecidomyidce. — Members of this family have mostly been 

 found in amber, there being no record of them in Mesozoic times. 



Fam. Syrphidce. — It is somewhat doubtful if this family is really 

 represented in time earlier than the Tertiary. Two species have 

 been referred to the Syrphidce from the Mesozoic rocks ; one 

 from the renowned rocks of Solenhofen, which, according to Weyen- 

 bergh, is a Cheiiosia, 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, Cheilosia, Volucella, Phingia, 

 Syrphus^ 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. 



