416 Mr. G. M. Thomson on two new 



obtained by the dredge in from 4-5 fathoms in Dunedin Har- 

 bour ; and I have reason to believe that they are somewhat 

 rare species. 



The first belongs to the genus Arcturus, and approximates 

 very closely to A. corniger , Stebbing*, a species found at 

 Algoa Bay. After reading Mr. Stebbing's description of 

 this species, and comparing it with that found here, I am 

 inclined to think that he has only seen females. It is very 

 similar to the female of the new species, but differs consider- 

 ably from the male. 



The species found here, which I propose to call A. tuber- 

 culatus, differs in the following general respects from A. 

 corniger : — The superior antennae are four-jointed, having a 

 large broad basal joint, and they extend considerably beyond 

 the extremity of the second joint of the inferior antennae. At 

 the extremity of the terminal joint there occur several minute 

 jointed appendages, regarding the function of which I am 

 quite ignorant. The fourth segment of the body, which in A. 

 corniger is produced upwards into six cone-like swellings, 

 bears in the male of the local species one stout conical tubercle 

 near each extremity (the anterior one being trifid), while in 

 the female it has ten pointed tubercles. The branchial oper- 

 cula are very long, and extend to the extremity of the abdo- 

 men. The following is a specific description of this interest- 

 ing form. 



Arcturus tuberculatus^ sp. nov. 



Male. Body rather robust. Head very indistinctly sepa- 

 rated from first segment of body, its antero-lateral margin 

 produced forward, apex crowned with a two-lobed tubercle. 

 Three anterior segments also produced upwards into acute 

 tubercles. Fourth segment smooth, bearing a single stout 

 spine at each end on the median line, the anterior one being 

 trifid. Superior antennae reaching beyond the extremity of 

 second joint of inferior ; basal joint stout ; second and third 

 short ; fourth as long as the two preceding, and bearing 

 several jointed appendages, each consisting of a minute basal 

 joint and a slender narrow lamella. Inferior antennae rather 

 longer than first four body- segments ; first and second joints 

 short ; third and fourth long, not ciliated, but with rows of 

 minute tubercles on the under margin ; flagellum three- 

 jointed, sparingly ciliated, with a row of acute spines or 

 serrations on its inner margin. 



These sharp teeth are present on the antennae of both sexes, 

 and must materially assist the animal in grasping its prey ; 



* Ann. & Mag. Nat. Hist. 4th ser. vol. xii. p. i»7 (1873). 



