ISCHIODONTUS. 317 



I. g?iseijpilis, the prosternal sutures, as in Crepidius, are not, or very feebly, grooved in 

 front ; in three, /. erythroderus, I. melas, and I. ntfivent?is, the sides of the mesosternal 

 cavity are rapidly and obliquely declivous, these insects forming a transition to the 

 genus Sjnlits ; and in one, /. aterrimus, a close ally of I. melas, the mesosternum is 

 formed as in those species here placed at the end of Atractosomus. Good sexual 

 characters are to be found in the form of the antennae in nearly all the species with a 

 large third joint (I. carinicomis and its allies excepted) to the antennae ; but in those 

 with a small third antennal joint there is very little sexual difference, the antennae 

 being comparatively short in both sexes. In all the species here referred to Ischio- 

 dontus the prosternal process is sharply angulate before, as well as at, the apex ; and 

 the posterior coxal plates are angularly widened, in some species with a triangular 

 dilatation behind, opposite the point of insertion of the femora. In I. carinicomis and 

 some few South-American forms the antennas are very distinctly carinate. 



A. Antennae with the third joint nearly or quite as large as the fourth. 



a. Mesosternum with the sides of the cavity not or feebly raised, gradually 

 declivous ; prosternal sutures (except in /. atrocaruleus, I. resplendens, 

 I. marginatus, and /. denticornis) deeply grooved in front. 

 a' . Antennae carinate, not much longer in the male than in the female . . Species 1. 

 b'. Antennae not carinate, much longer in the male than in the female. 

 a". Upper surface not metallic. 



a'". Punctures on the head and prothorax simple or feebly umbilicate 



(umbilicate on the head in some of the species) Species 2-16. 



b'". Punctures on the head and prothorax distinctly umbilicate . . . Species 17-22. 

 b". Upper surface partly metallic. 



c"'. Prothorax black (variable in /. chloropterus). 



a 4 . Elytra bluish-black, dull Species 23. 



b\ Elytra violaceous ; abdomen black Species 24. 



c\ Elytra brilliant violaceous, metallic green at the base and apex ; 



abdomen rufous Species 25. 



d l . Elytra aeneous or green, or with an aeneous lustre Species 26-28. 



d'". Prothorax rufous or rufo-testaceous, the elytra aeneous or green . Species 29-31. 

 ef". Prothorax and elytra ferruginous or pitchy-red, the sides of the 



elytra infuscate and with an aeneous lustre Species 32. 



c". Upper surface metallic — the head and prothorax aeneous, the elytra 



green Species 33. 



b. Mesosternum with the sides of the cavity considerably raised, obliquely 

 declivous. 

 /"'. Prosternal sutures not grooved in front; antennae slender; body 



very elongate, cuneiform Species 34. 



g m , Prosternal sutures deeply grooved in front; antennae rather 

 broadly widened. 

 e 4 . Prothorax more or less rufous ; elytra black Species 35. 



