Siaphi/Unidce of tlie Amazon Valley. 125 



width ; just a little broader in front, and the sides a little 

 sinuate ; on each side of the middle is an irregular line of 

 about nine punctures, and other punctures are scattered 

 along the sides, especially near the front part. Elytra 

 about the length of the thorax, blue, Avith a grey pubes- 

 cence at the base and near the extremity, moderately 

 closely punctured. Hind body yellow, with the 2nd seg- 

 ment darker ; it is almost impunctate, and very sparingly 

 pubescent above, beneath distinctly but rather spai'ingly 

 punctiu'ed, and with a fine long pubescence. Legs yellow, 

 with the coxa) pitchy. 



The characters of the male are very complicated and 

 most remarkable. The front tibise are dilated towards 

 the apex, and somcAvhat concave on the inner side ; the 

 three basal joints of the front tarsi are a little dilated. The 

 dorsal plate of the 7 th segment of the hind body has three 

 sinuses at the hind margin ; the middle one is the broader, 

 but is not formed by the margin being cut away, but by 

 its being turned downwards ; at the base of this turned- 

 down portion are two sharp teeth, placed near to one 

 another ; from the extremity of this turned-down part pro- 

 ject two vertical processes. The ventral plate of the same 

 segment is a little produced, and has a deep incision or 

 notch in the hind margin ; along each side of this notch it 

 is broadly impressed. The lateral lobes of the 8tli seg- 

 ment are modified in a most extraordinary manner ; each 

 terminates in three processes, — a broad, truncate, central 

 one, armed on the inner side with two rows of file-like 

 asperities, and a long, slender, somewhat curved process 

 on each side. The body of the asdeagus terminates in 

 a produced point or beak, and is furnished beneath 

 with a ligula longer and broader than the beak, and 

 densely set Avitli black asperities on each side, towards 

 the end. 



Ega ; tw'o males. 



Obs. — This species is undoubtedly closely allied to 

 St. venustus, Er., from Cayenne, but I cannot make the $ 

 characters agree with Erichson's description. These male 

 characters are the most extraordinary I have met with 

 in any Coleopterous insect. 



Xanthopygus. 



This genus, like the tw^o preceding ones, is due to 

 Dr. Kraatz ; but milike them, it seems to be composed of 



