56 



in doubt, and shall remain so till you answer my letter, for I 

 have not been able to see a fork. 



HARRIS TO HENTZ. 



MILTON, Feb. 20, 1829. 



Since I wrote to you I have found the genus Cylidrus, with 

 Latreille's definition of it, in that valuable work, the ISTouveau 

 Dictionnaire d'histoire naturelle, which is in the college library. 

 It appears to be closely related to Tillus, and probably your 860 

 belongs to it. Not having seen any of the genera belonging to 

 Kirby's section Serricornes of the family Clerii, except Enop- 

 lium, I do not feel fully competent to decide upon your 874, 

 which should be closely compared with the other peiitamerous 

 genera of that section to decide whether it is admissible, or 

 whether it should not rather constitute a new genus. The plan 

 pursued by Mr. Kirby (Linn. Trans. Vol. XII., pp. 340, 389) 

 would facilitate the determination ; but the number, division, 

 and pulvilli of the tarsal joints, with the form of the mandi- 

 bles, eyes and nails, should also be taken into the account. 

 Latreille must be mistaken when he says that in Thanasimus 

 there are only four joints visible in the tarsi. In T. formicarius, 

 which is the type, there are certainly five distinct joints, as also 

 in ichneumoncus, nigrifrons, and your 239. [239 Hentz MSS. 

 Cat&\.= Thanasimus putans.'] Thanasimus then appears to be 

 an osculant genus, connecting the pentamerous Cleridce with the 

 heteromerous genera of that family, through the genus Clerus, 

 with which it agrees in its clavate antennas. Probably your 240 

 [240 Hentz MSS. CatsH.=Tillus terminalis Say MSS.] is the link 

 in the chain of affinities uniting Thanasimus with the pen- 

 tamerous Serricornes. It is worthy of remark that in Nccrolia 

 the tarsi are apparently trimerons, the first joint being hid by 

 the base of the second, and the fourth entire, and concealed in 



