298 Mr. S. W. Kemp on neio Species of 



Olivl, a species vvliich is comparative! j abundant in the 

 Mediterranean at depths of 20 or 30 fathoms. 



The genera of the Crangonida3 are, as all who liave studied 

 them will admit, in a deplorable state of confusion. Ortmann 

 and, more recently, Stabbing have done much to evolve order 

 out of chaos, but the classitieation, even of the species 

 occurring off our own coasts, is still far from satisfactory. 



Stebbing has pointed out * that Pontocaris, Sp. Bate, is a 

 synonym oi ^(jeon (type sp. cataphractus) , which is distinct 

 from most if not all other genera of Crangonidaj by the fact 

 that the inferior extremities of the gills are turned forwards, 

 the whole gill being C-shaped. 



This feature, however, is not present in the two British 

 species, sculptus, Bell, and fasciatus, Risso, which liave 

 hitherto been placed in thisgenns. It may also be mentioned 

 that the first trunk-legs of these two species do not bear at 

 their base the small exopod which is present in cataphractuft. 



I would suggest that, at any rate until the genera have 

 been fully revised, sculptus and fasciatus should be referred 

 to PhilocheraSf Stebbing (nora. nov. vice Cheraphilus), for 

 the distinction as to the number of brancliige, which has been 

 put forward as separating ^c/eon and Philocheras, seems to 

 be based on a misunderstanding. 



The presence or absence of an exopod at the base of the 

 first pair of trunk-legs is a characteristic which has rarely 

 been taken into account by those who have treated of this 

 family ; it should be noted that although Alcock has stated f 

 that no such exopod exists in the genus Pontophilus, it is 

 nevertheless present in P. spinosus (type sp. of geuus) and 

 also in P. norvegicus. 



The British genera of Crangonidie may be thus defined in 

 tabular form : — 



, ] Second pair of trunk- legs simple 1. Sahinea. 



I Second pair of trunk-legs chelate, 2. 



1 Second pair of trunk-legs about equal in length to 

 first 2. Cramjon. 

 Second pair of trunk-legs shorter than first, 3. 

 i Second pair of trunk-legs scarcely one thii-d the 

 length of first 3. Fontophilus. 

 Second pair of trunk-legs about three quarters the 

 length of first, 4. 

 ! Inferior apices of gills turned forwards, small 

 exopod at base of tirst pair of trunk-legs 4. JEgeon. 

 Inferior apices of gills turned backwards, no exopod 

 at base of first pair of trunk-legs 5. Philocheras. 



* Stebbing, ' South African Crustacea,' pt. i. p. 48 (1900). 

 t ' Descrip. Cat. Macrura in Indian Museum,' p. 114 (1901). 



