Ixxxiv NATURAL HISTORY. 



cellany," he. cit. It was taken near the Scottish coast; and Dr. Leach received 

 an imperfect specimen from the Firth of Forth, but it appears to be of very rare 

 occurrence in those parts. During one of our former voyages, we found it near 

 the island of IglooHk in considerable numbers, associated with the preceding and fol- 

 lowing species. Some specimens were obtained by us, through a hole in the ice, 

 at Felix Harbour, in the very depth of winter. 



The general form of the rostrum agrees with that figured by Dr. Leach, but 

 many have it simply emarginate at the apex, and not serrulate. 



It differs from the two following species in the dentations of the carina of the thorax, 

 extendino- along its whole length ; and in the upper part of the third segment of the 

 body being produced posteriorly in a strong spine. 



5.— HIPPOLITE BOREALIS. («. s.) 



Plate B, fig. 3. 



Hipp, thoracis dimidio posteriore laevi, anteriore sub-carinato, raargine anteriore utrinque bi-spinoso. 



Tlie principal differences, as compared with the A. (H.) Polaris of Sabine, consist in 

 the absence of, or very slightly marked, dentations on the thoracic carina ; in having 

 only two spines, instead of three, on either side of the anterior margin of the thorax 

 (that at the junction of the lateral margin being wanting in H. Polaris) ; in the superior 

 antennae being proportionally longer ; and in being of a paler yellow colour, without 

 the red spots and markings of the H. Polaris. As in the specimens of H. Polaris 

 obtained by me, the middle lamella of the tail has from eight to ten minute spines along 

 each side, and is terminated by several strong setae, the margins of the rest of the plates 

 of the tail are beautifully ciliated, excepting on the exterior edge of the lateral plates, 

 which are toothed at their posterior angle. 



Dr. Leach takes his specific characters from the rostral dentations, but these, as 

 Captain Sabine justly remarks, in his description of A/p/ieiis (liippo/ite) Polaris, 

 ao-ree in no two specimens of that species, as to number, nor the rostrum as to shape. 



H. Borealis was found associated with the preceding species, and was dredged up 



