ATYLIDAE 185 



Mouth-parts normal. Mandibular palp with 2nd and 3rd joints subequal. 



Gnathopod 1, 2nd joint setulose on front margin, setose on hind margin, 5th tri- 

 angular, 6th ovate, longer than 5th, palm oblique, not defined except by two spines, 

 front margin with transverse rows of setae, lower margins of 4th-6th joints strongly- 

 setose. Gnathopod 2 resembling gnathopod 1, but more slender. 



Peraeopods 1 and 2, 2nd joint linear, 6th longer than 4th and nearly equal to 2nd. 

 Peraeopod 3, 2nd joint basally expanded, tapering distally, hind margin serrulate and 

 setose basally, concave distally with a few setules. Peraeopod 4 similar to peraeopod 3, 

 but longer, 2nd joint similar but anterior margin more convex and rather strongly 

 spinulose. Peraeopod 5 slightly longer than 4th, 2nd joint ovate, hind margin convex 

 and serrulate throughout. Dactyls of peraeopods 3-5 pointing forwards. 



Uropod 1, upper margin of peduncle spinulose, rami subequal to peduncle. Uropod 

 2 shorter than uropod 1 , peduncle shorter than that of uropod 1 , outer ramus defective 

 on both sides. Uropod 3 extending as far back as uropod 1, peduncle short, half the 

 length of that of uropod 2, both rami narrow, tapering, subequal, with spinules on both 

 margins, and in addition plumose setae on inner margins. 



Branchial lamellae simple, with slight indications of pleating near bases. 



Dentate form 



Occurrence: St. 222. Cape Horn. 1 ^ 15 mm., 2 $$ 15-16 mm. 



Description. This form does not differ from the typical form except in having the 

 dorsal carina produced in pointed teeth on pleon segments 1-3 and 6, as well as on pleon 

 segment 4; all the peraeopods shorter and stouter; and the branchiae slightly more 

 pleated basally. 



Remarks. This is a very interesting rediscovery of a species described from a single 

 S, and apparently not since observed. Bate's description proves to be good and his 

 figure shows moderately well the features which distinguish this species. 



It will be noted that the shape of side-plates 4-6, especially of the dentate form, bring 

 this species near to smitti (cf. Sars, 1895, pi. clxv, fig. 1), from which it is distinguished 

 by the anterior margin of head, 2nd joint of peraeopod 5, and the telson. 



The lower margins of pleon segments 1-3 in these specimens are not actually serrate 

 as Bate describes them, but the submarginal groups of spinules produce the same ap- 

 pearance (under a low magnification) as is shown in Bate's figure. 



The variable development of the dorsal teeth and of the pleating on the branchiae 

 indicates that a revision of the northern species might result in the reduction of 

 species. 



Distribution. Hermite Island. 



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