114 Mr. W. Thompson on new species of British Crustacea. 



third segment, and then becoming suddenly very much con- 

 tracted, and of ahuost equal size throughout. The process of 

 the third segment of the abdomen is very prominent. 



Colour brown with a reddish tinge in places. 



Length about 10 lines. 



This species is very easily distinguished by the armature of 

 the head, form of the abdomen, and the shape and armature of 

 the rostrum, in which it approaches no other described British 

 species. I obtained it in four fathom water, stony bottom, 

 Weymouth Bay. 



I have named it after Dr. J. E. Gray, the Keeper of the Natural 

 History Department of the British Museum. 



HiPPOLYTE MiTCHELLi (mihi). Mitchell's Hippolyte. 

 PI. VI. fig. 4. 



Spec. Char. Rostrum (fig. 4 a) straight, acuminate, without a 

 spine on the upper portion ; beneath with a three-toothed carina, 

 and a small tooth near the apex. 



Carapace not at all gibbous, terminated by a straight and 

 elongated rostrum, without a tooth on its upper edge; beneath 

 there is a short carina carrying three teeth : a small tooth is 

 placed near the apex. A small tooth is placed each side of the base 

 of the rostrum over the orbit. Scale of the external antennae 

 not very broad, but long, extending beyond the rostrum, with 

 an external tooth, which is placed at one-fourth the length of 

 the antennae from the extremity. 



Length 16 hues. 



Colour a beautiful clear and dark green. 



I obtained nine individuals from amongst a parcel of Hippolyte 

 Jfhitei brought me on the 2nd of July, 1853. 



This species at first sight might be taken for H. Whitei; it 

 is, however, larger, and the teeth on the rostrum are more 

 numerous. 



I was at first disposed to consider this as only a variety of 

 H. Whitei, but the fact of finding so many, and all perfectly 

 agreeing, decided me in admitting it as a new species. 



I obtained this species by dredging ; none carried ova ; it was 

 taken in four to six fathom water, on a weedy and stony bottom, 

 Weymouth Bay. 



I beg to name this species after Mr. Mitchell, the indefatigable 

 Secretary of the Zoological Gardens, and the successful pro- 

 moter of the Marine Vivarium, as it is owing to the impetus 

 given to dredging by the demand for marine life, that I am 

 indebted for all the new species now described. 



