5284 



Crustacea. 



pointed in consequence of this form of articulation. The lateral tufts 

 of setae to the abdominal rings I never observed in A. stirynchus; but 

 they are very apparent in this. The central caudal plate in this is 

 quadrangular, while in A. stirynchus it is elongated- triangular. These 

 alone are, I think, sufficient marks of variation to justify the idea of 

 specific distinction. 



My sis Oberon. 



Specific characters. Rostrum obtusely triangular, reaching as far 

 as the circumference of the cornea; middle caudal plate lanceolate; 

 apex rounded, and the rounded portions armed with two diverging 

 teeth. 



Habitat. In sheltered pools, and margins of overhanging rocks 

 near low-water mark, in August. Mount's Bay. 



Mvsis Ob K RON. — 1. Animal. 2. Dorsal view of rostrum, &c. 

 dages of abdomen. 5. Feet. 



3. Caudal extremity. 4. Natatory appen- 



This elegant species is not very uncommon during the warm wea- 

 ther of August, and it is occasionally found in July if there is much 

 sunshine and quiet. It is most commonly found in clear pools with 

 rocky bottoms, and under overhanging rocks in the tide-way where 

 there is great clearness of the water and no muddy soil. It is now 

 more than two years ago since 1 first detected it, and ascertained 

 what I consider to be its specific differences. At that time I thought 

 it to be very rare ; having, however, lately fished with coloured nets, 

 it has proved to be much more common than was at first anticipated. 



