116 



DECAPOD A. 



BRACHYURA. 



POBTUNID-dB. 



1'ORTUNIDA.. 



HENSLOW'S SWIMMING-CRAB. 

 PolyMus Henslowii. Leach. 



Polybius Henslowii, LKACH, Malac. Brit, t, ix. B. EDWARDS. Crust. I. p. 439. 



THIS species, the only one of the genus at present 

 known, exhibits the natatory structure to the greatest ex- 

 tent of any of the British examples of this family. The 

 carapace is remarkably flat, even in the female, and the 

 regions are very indistinctly marked ; it is all over minutely 

 granulated. Its form is nearly orbicular ; the latero-anterior 

 margins, with the orbits and front, forming a semicircle, 

 and the latero-posterior margins being but little contracted : 

 the front is flat, and has five teeth, the external of which 

 on each side belongs to the orbit : the latero-anterior 

 margin has five flat teeth, the points directed somewhat 

 forwards. 



