Genera and Species of Phytophaga. 243 
gibbosity of the elytra, this part being much produced in the 
present species, and forming a short flattened spine; in bivitti- 
pennis, on the other hand, it is very short, and approaches more 
nearly to B. peregrina and other allied species. 
Thorax twice as broad as long; sides obliquely dilated, very 
slightly rounded ; surface opaque, obsoletely punctured, impressed 
along the base with four or five large fovez ; anterior half of the 
disc deeply excavated, leaving the medial line as a distinct longi- 
tudinal ridge. Scutellum smooth, impressed in the middle with 
a large deep fovea. 
