52 BRITISH TYROGLYPHID^E. 



have proposed dividing the cephalothorax into two 

 divisions, the anterior of which they call the " Capitu- 

 lum ; " I cannot say that I like this term ; it is too 

 similar to " caput," and seems to identify the part 

 spoken of with the caput of the Insecta ; but they are 

 not homologous ; in such Acari as are possessed of eyes 

 these organs are not upon the so-called capitulum but 

 on the cephalothorax behind it, and I confess that I do 

 not recognise as correct a caput or capitulum which 

 does not include the eyes, or any part of the great 

 nerve ganglia. The fact is that the term is practically 

 used for the maxillary lip or hypostome and whatever 

 organs happen to lie above it ; that is to say on the 

 dorsal side of it ; in those numerous cases where this 

 portion of the cephalothorax is divided from the pos- 

 terior portion by a constriction or flexible band or 

 suture ; this is not the case in any of the Tyrogly- 

 phidse which I am acquainted with, unless the genera 

 Histiostoma or Lentungula can be considered instances, 

 which I hardly think they can be. The old term is the 

 " rostrum," and on the whole I think it should be pre- 

 served although I admit that it is a vague term which 

 has been used in different senses by different authors ; 

 and which can only be taken to mean the anterior part 

 of the cephalothorax ; because although in some cases, 

 such as the Ixodidae, a perfectly clear demarcation 

 exists between the rostrum (which term in this family 

 is usually used for the maxillary lip only) and the 

 remainder of the cephalothorax; yet in the larger 

 number of the Acari the demarcation is lost and it is 

 impossible to say where one ends and the other begins : 

 this difficulty is not cured by calling the rostrum a 

 capitulum in the cases where the demarcation is evi- 

 dent; for these instances fade into those where it is 

 entirely absent by insensible degrees. 



