298 Prof. J. C. Schiodte on the 



lobe of the right mandible fits into the cleft between the outer 

 and inner lobes of the left ; so that the cutting is done bj three 

 saw-blades — two from the left side and one from the right, 

 which latter cuts in between the two former. 



This remarkable combination obtains with small variations 

 through the entire series of Hyperini, which otherwise presents 

 such different forms. With reference to its principal charac- 

 ter, the fitting of the mandibular lobes into a groove or hollow 

 in the upper lip, the Amphipoda of this type may be called 

 Piezognatha. 



21. We have then the following formulas for the three 

 types in the structure of the mouth in biting Amphipoda : — 



Eleutheeognatha. 



Mandibulge trigonae, condylo articulario antico carentes. 

 Labrum planiusculum, transversum, simplex. 



Trochalognatha. 



Mandibular productse, condylo articulario instructs antico, 



acetabulo epipharyngis accommodato. 

 Labrum crassum, conicum, simplex. 



Piezognatha. 



Mandibulte producta3, condylo articulario antico carentes, mala 



exteriore fossse transversse labri accommodata. 

 Labrum planiusculum, transversum, duplex. 



22. Amongst the series of forms exhibiting the eleuthero- 

 gnath type, there are several which simulate more or less 

 strikingly the build of other types. One of the most remark- 

 able is StegocephaluSy reminding us in general appearance of 

 the trochalognath Anont/x, whilst its enormously developed 

 face and the armament of the mandibles approach more to the 

 piezognath Hyperia. 



The clypeus, labrum, palate, two pairs of maxillge, and the 

 maxillipeds, as well as the mandibular springs of the lower 

 lip, correspond in all essential respects to the general fea- 

 tures of the type. The upper lip is bilobate, the right-hand 

 lobe larger than the left. But the mandibles are quite 

 without grinding-teeth, the right mandible also without an 

 inner lobe ; and though the left mandible possesses the hard 

 branch of the latter, which has a long finely serrate margin, it 

 lacks the membranaceous digitiform appendages ; the outer 

 lobes of both mandibles have each a long, curved, finely 

 serratulated edge, almost as in Hyperini, but with the essen- 

 tial difference that all the saw-teeth are here equally large, 



