»326 J. W. Half: Head A^ipeiulages in the Crayfish. 



right side, and its anterior limit formed by the interantetmal spine 

 is inclined over towards the right side. 



The aiKfcnmi and the mandible -avq situated mucli closer to one 

 -anotlier on tlie right side than they are on the left, for not only 

 is the right mandible attached more anteriorly than the left, but 

 also the riglit antenna is situated more posteriorly than the left. 

 These positions have obviously been taken up owing to the absence 

 of the hard stei-nal portion on the right side. The interantennal 

 sjnnt is broader from side to side, but shorter in length than in a 

 normal specimen, so the distance between the labrum and the tip 

 of the interantennal spine is much shorter than it should be. 



The left antt7inuU\ has apparently become pushed away from its 

 own side by pressure of the antenna against it, due to the shifting 

 over of the epistoma to the right side. This has consequently dis- 

 placed the riglit antennule and driven it further back, so instead 

 of lying on a level with the left one, it now appears lower down, 

 i.e., more on a level with the antennae. 



All other appendages of the body appear to be (]uite normal. 



EXPLANATION 0¥ PLATE XV. 



Pig. 1. — Dorsal view of head of ciayfish, showing position of 



antennules. 

 rig. 2. — Ventral view, showing positions of the different parts — 



the first and second maxillae and the first maxillipede are 



hidden by the second maxillipede. 



