:n- 



BY R. J. TILLYAKD. 367 



dominant position within the Blattoidea during the Lias. We 

 should, therefore, not be at all surprised to find that the cock- 

 roaches from Ipswich, with the single exception of the fine genus 

 Austromylacrites Tillyard, previously described (2, p. 13), fall 

 naturally into this family. 



Of the eleven specimens here dealt with, only two (Specimens 

 121«-6 and 152) are not named, the former being too poorly pre- 

 served, the latter too fragmentary. Of the remaining nine, two 

 cannot be placed with certainty in their correct genera; these 

 are Specimens 216 and 262, the former being a nearly perfect 

 clavus or anal area only, while the latter has neither humeral 

 area nor anal area clearly preserved. The remaining species may 

 be arranged within three genera, on well-defined characters, as 

 shown in the following key : — 



'Length of humeral area, from base to apex, distinctly less 



than that of anal area Triassoblatta, n.g. 



Length of humeral area, from base to apex, at least equal to 



that of anal area 2. 



'Medium-sized tegmina (about 13 mm. long) with the main 

 stem of R fairly strongly double-curved, so that its lowest 

 point of dip reaches almost to the middle line of the 



(2)-^ tegmen Samaroblatta, n.g. 



Small tegmina (less than 10 mm. long), with the main stem 

 of R very slightly curved, its lowest point of dip lying well 

 above the middle line of the tegmen Austroblattula, n.g. 



Genus Triassobi.a t t a, n.g. (Text-figs. 30a, 31-33). 



Medium-sized to large tegmina from 12 to 21mm. in length. 

 Humeral area narrow to moderately wide; distinctly less in 

 length, from base to apex, than is the anal area. Sc consisting 

 of a group of sectors, one of which borders the costal area dis- 

 tally, with or without extra branches on that area, but always 

 with at least one branching sector placed distad from it. Main 

 stem of R with very weak double-curving, so that its lowest 

 point of dip lies well above the middle line of the tegmen, and 

 the most distal branch of II reaches almost to the apex. Anal 

 area somewhat cultriform, well-defined, with some at least of the 

 anal veins forking well before their distal ends. 



