276 Mr. C. Spence Bate on the 



group from thirteen different places ; and in every one I was 

 able, upon close examination, to find the eyes very distinct, 

 though singularly situated. Moreover there is a variation in 

 form and position that gives them a value in classification, 

 particularly when taken into consideration with the relative 

 forms of the several pairs of pereiopoda. 



The dorsal surface of the several species of this group is 

 flattened and depressed, and the anterior margin is tolerably 

 straight ; the central tooth, which is sometimes single and 

 sometimes double, is never directed forwards in the form of a 

 rostrum, but upwards and obliquely forwards. In the anterior 

 margin on each side there is a deep cleft in the dorsal surface, 

 in which the eye with its peduncule is lodged ; the an- 

 terior extremity being directed forwards, outwards, and down- 

 wards, is covered over by the lateral projecting wings of the 

 carapace. It appears to have two points of vision, the one 

 upwards by the dorsal surface, the other downwards and out- 

 wards by the lens at the extremity of the peduncle. But 

 these several points are liable to vary in degree. In some 

 the dorsal notch is almost non-existent, in others it is very 

 deep ; and it is by this variation, taken in connexion with the 

 power of change in the form of the pereiopoda, that I 

 purpose classifying the several species of this interesting 

 group. 



POLYCHELES, Heller. 



(Crust, des siidl. Europa.) 



In this genus I accept the author's definition, that it has 

 the anterior four pairs of pereiopoda chelate and the fifth 

 simple. But instead of saying that the eyes are rudimentary, 

 I assert that they are immovably lodged in a notch in the dorsal 

 surface of the carapace, with the anterior extremity projecting 

 beneath the antero -lateral wing of the carapace. 



Pentacheles, n. g. 



All the pereiopoda are chelate, and the eyes are lodged 

 immovably in a notch in the antero-dorsal surface of the 

 carapace, with the anterior extremity projected beneath the 

 antero-lateral wing-like extremity of the carapace. 



WiLLEMOESIA, Grote. 

 (Nature, October 1873.) 

 All the pereiopoda chelate, and the eyes immovably situ- 



