12 DR. BRACKENRIDGE CLEMENS' LETTERS. 



this tribe, I was, of course, entirely unable to locate it, until a 

 few weeks since, during a short visit to Philadelphia, I was 

 able to consult hastily, at the Academy of Natural Sciences, 

 a copy of your excellent work on " Tineina," forming part of 

 Insecta Britannica. It is a source of regret with me that 

 I cannot obtain a copy,' having been assured it is out of 

 print. However, by carefully comparing my representation 

 of the neuration of this leaf-miner, with the pterological 

 delineations in that volume, I was at once enabled to refer 

 it to the family LithocoUetidce. Then, turning to your re- 

 marks on the family, satisfied myself at once as to the correct- 

 ness of the reference, having carefully examined the insect 

 before leaving home. You are probably prepared for any 

 degree of temerity on the part of the young student, but will 

 you not be surprised if I doubt whether it belongs to the 

 genus Lithocolletis? This doubt, however, is dependent on 

 the question whether the neuration of Lithocolletis Messani- 

 ella is correctly and accurately delineated : I do not, however, 

 for a moment doubt it with no evidence to the contrary. If 

 you will refer to it in the above work you will perceive, that 

 whilst mine is evidently of the same type, there is a marked 

 modification in the neuration of the anterior wings. The 

 sub-costal nervure in mine throws off, near the apex of the 

 wing and in quick succession, two marginal nervules, an 

 apical and post-apical nervule, whilst the median is entirely 

 icanting. I am unable, at present, to determine the value, 

 if it has any, of this modification. I have no other speci- 

 mens of this family with which to compare it. But my 

 investigations up to this time, with regard to the value of 

 neuration as a basis of classification, and its significance as a 

 " dominator * character," imperfect though they necessarily 

 are, in consequence of my limited entomological resources, 

 have constantly indicated to me the existence of three 

 general laws, which, however, I do not wish to be nnder- 



* In his next letter Dr. Clemens proposed to substitute the word " predomi- 

 nant" for " dominator." H. T. S. 



